United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued January 19, 2024             Decided November 12, 2024

                         No. 23-1067

              MARIN AUDUBON SOCIETY, ET AL.,
                      PETITIONERS

                               v.

 FEDERAL AVIATION ADMINISTRATION, U.S. DEPARTMENT OF
   TRANSPORTATION AND NATIONAL PARK SERVICE, U.S.
             DEPARTMENT OF THE INTERIOR,
                    RESPONDENTS


              On Petition for Review of an Order
            of the Federal Aviation Administration



     Peter T. Jenkins argued the cause for petitioners. With him
on the briefs was Paula Dinerstein.

    Justin D. Heminger, Attorney, U.S. Department of Justice,
argued the cause for respondents. With him on the brief were
Todd Kim, Assistant Attorney General, and Robert P. Stockman,
Attorney.

    Before: SRINIVASAN, Chief Judge, HENDERSON, Circuit
Judge, and RANDOLPH, Senior Circuit Judge.
                               2

     Opinion for the Court filed PER CURIAM with respect to
Parts I and III.

   Opinion for the Court filed by Senior Circuit Judge
RANDOLPH with respect to Parts II and IV.

   Concurring opinion filed by Senior Circuit Judge
RANDOLPH with respect to Part IV.

     Dissenting opinion filed by Chief Judge SRINIVASAN with
respect to Parts II and IV.

                               I.

     The Federal Aviation Administration is an agency within
the Department of Transportation. The National Park Service is
an agency within the Department of the Interior. The National
Parks Air Tour Management Act of 2000 requires these two
agencies to work together in developing plans regulating tour
flights over national parks throughout the United States. See

 801–809, 

, 185–94 (2000)
(codified as amended at 

 and note).

    To that end, the Agencies issued an Air Tour Management
Plan governing tourist flights over four national parks near San
Francisco, California: the Golden Gate National Recreation
Area, Muir Woods National Monument, San Francisco
Maritime National Historical Park, and Point Reyes National
Seashore. The Agencies determined that there was no need to
prepare an environmental analysis under the National
Environmental Policy Act because their Plan, as compared to
what existed, would cause minimal additional or no
environmental impact.
                                3


     A group of organizations and one area resident brought this
direct review action to set aside the Agencies’ Plan.

                                A.

     The National Parks Act requires commercial air operators
to obtain approval from the FAA before conducting tourist
flights over a national park. 

(a)(1)–(2). The
FAA may not approve an operator’s application without first, “in
cooperation with” the Park Service, developing an Air Tour
Management Plan for the park. See 

 § 40128(a)(2)(D).

     “The objective of any [Plan] shall be to develop acceptable
and effective measures to mitigate or prevent the significant
adverse impacts, if any, of commercial air tour operations upon
the natural and cultural resources, visitor experiences, and tribal
lands.” Id. § 40128(b)(1)(B). Such a Plan can prohibit air tours
altogether or it may impose lesser limitations, including
particular “routes, maximum or minimum altitudes, time-of-day
restrictions,” “maximum number of flights per unit of time,” and
“mitigation of noise, visual, or other impacts.”                Id.
§ 40128(b)(3)(B). In formulating their plan, the Agencies must
comply with the National Environmental Policy Act, id.
§ 40128(b)(2), and their Plan must go through notice and
comment procedures, id. § 40128(b)(4)(B).

      The Parks Act specifies that the FAA “shall make every
effort to act on any [commercial air tour operator’s] application
. . . and issue a decision on the application not later than 24
months after it is received or amended.” Id. § 40128(a)(2)(E).
Recognizing that the process could take substantial time,
Congress directed the FAA to enable existing air tour operators
to apply for “interim operating authority.” Id. § 40128(c)(1).
Interim operating authority enables operators already conducting
air tours to continue doing so while the Agencies develop
                               4

a Plan. Interim operating authority terminates 180 days after a
Plan is put in place. Id. § 40128(c)(2)(E).

    The Parks Act also allows the Agencies to enter into
voluntary agreements with tour operators in lieu of establishing
a Plan. Id. § 40128(b)(7). A voluntary agreement need not
undergo formal notice and comment procedures and is not
subject to NEPA. See id. § 40128(b)(7)(C).

                              B.

     NEPA requires federal agencies to prepare “a detailed
statement” assessing the environmental impacts of all “major
Federal actions significantly affecting the quality of the human
environment.” 

(2)(C). ‘‘‘NEPA itself does not
mandate particular results’ in order to accomplish these ends.
Rather, NEPA imposes only procedural requirements on federal
agencies with a particular focus on requiring agencies to
undertake analyses of the environmental impact of their
proposals and actions.” Dep’t of Transp. v. Pub. Citizen, 541
US. 752, 756–57 (2004) (quoting Robertson v. Methow Valley
Citizens Council, 

 (1989)).

     The detailed environmental impact statement must analyze
the “environmental impact of the proposed action,” any
unavoidable “adverse environmental effects” of the action, and
potential alternatives to the action. 

(2)(C)
(1970) (amended June 3, 2023).

     According to regulations issued by the Council on
Environmental Quality—about which more later—if the
proposed action “[i]s not likely to have significant
[environmental] effects or the significance of the effects is
unknown,” then the agency can prepare an environmental
assessment. 

(a)(2) (2020); see generally 42
    

. An environmental assessment under CEQ’s
detailed regulations is a more concise document through which the
agency either (i) determines that the action will have significant
environmental impacts of a kind requiring an environmental
impact statement or (ii) makes a finding of no significant impact,
in which case no environmental impact statement is needed. 

 (2020); see also 

 § 1501.6 (2020).

     CEQ regulations also state that the agency may forgo
preparing an environmental impact statement or an
environmental assessment if the proposed action is
“categorically excluded” from NEPA’s usual requirements
because it “[n]ormally does not have significant effects” on the
environment. Id. § 1501.3(a)(1) (2020).

                               C.

     Congress, as noted, directed these Agencies to “make every
effort” to complete a Plan within twenty-four months of an air
tour operator’s application. 

(a)(2)(e). The
Agencies, though, became mired in “infighting” and
“squabbles.” In re Pub. Emps. for Env’t Resp. (In re PEER),

 (D.C. Cir. 2020). As of 2020, “applications
[had] been pending at twenty-five parks for nearly two decades,”
but the Agencies had “fulfilled their statutory mandate at only
two,” albeit even in those instances by reaching voluntary
agreements with air tour operators rather than by establishing
Plans. 

 at 269–71.

      Because of the Agencies’ inaction, our court granted a
petition for a writ of mandamus to compel the Agencies to bring
all twenty-three parks with pending applications—including the
four parks at issue in this case—into compliance with the Act.

. Our court also retained jurisdiction to monitor the
Agencies’ progress. 

 at 275–76.
                               6


     In 2011, the Agencies announced their intent to develop a
Plan and prepare an environmental assessment for the Bay Area
Parks.    Notice of Intent to Prepare an Environmental
Assessment, 

 (July 28, 2011). No
environmental assessment was ever completed, however.

     That is because the Agencies halted the process for
developing Plans and environmental assessments/environmental
impact statements at ten parks—including the Bay Area
Parks—after Congress amended the Parks Act in 2012.
Termination of Previously Initiated Processes for the
Development of Air Tour Management Plans and Environmental
Assessments/Environmental Impact Statements for Various
National Park Units, 

, 55,060 (Sept. 3,
2020). The Agencies then formally “terminat[ed]” those
processes in September 2020. 

 The initial pause was “due to
a focus on other program priorities,” namely “the development
of Voluntary Agreements” with tour operators because those
agreements “do not require compliance with NEPA.” 

 The
Agencies then terminated the paused processes because, “[g]iven
the length of time since [they] were initiated and actively
worked, termination” would “allow the agencies to start anew
with the development of [Plans] and associated environmental
documents at these and other parks.” 

     Upon restarting the Plan process, the Agencies decided to
prepare a single Plan for all four Bay Area Parks. They did so
because of the “close proximity of the parks, including shared
borders,” and “the fact that the same operators conducted tours
over” three of the parks, with some routes “overfl[ying] multiple
parks.” U.S. Dep’t of Transp., Fed. Aviation Admin. & U.S.
Dep’t of the Interior, Nat’l Park Serv., Record of Decision: Air
Tour Management Plan for Golden Gate National Recreational
Area, Muir Woods National Monument, San Francisco Maritime
                               7

National Historical Park, and Point Reyes National Seashore 4
(Jan. 10, 2023) (Record of Decision).

      For purposes of their NEPA analysis, the Agencies used
existing air tours to determine the environmental baseline
against which they would assess the Plan’s environmental
impact. At the time, two companies possessed interim operating
authority to conduct flights over the Bay Area Parks. On paper,
those operators together had authority to conduct 5,090 tours per
year over the four Parks. Fewer flights were actually flown,
however, and the Agencies decided to use the average annual
number of actual flights to identify the baseline existing
condition. The Agencies calculated that the operators conducted
an annual average of 2,548 tours over Golden Gate and San
Francisco Maritime from 2017 to 2019, and that 143 of those
tours also flew over or close to Point Reyes. The Agencies
treated that average volume as the existing environmental
condition of the Bay Area Parks.

     The final Bay Area Parks Plan authorizes maintaining that
“existing condition,” albeit “with measures designed to mitigate
impacts [of the flights] on the Parks’ resources and visitor
experience.” 

. Thus, the Plan authorizes 2,548 tours
over Golden Gate and San Francisco Maritime, 143 of which
may also fly over Point Reyes, but with certain limitations. For
example, the Plan specifies the kinds of aircraft operators can
use, imposes daily flight caps, and alters existing routes and
schedules to avoid disturbing wildlife and impinging on visitors’
aesthetic experiences.

      The Agencies concluded that they did not need to prepare
an environmental assessment or environmental impact statement
for “[c]hanges or amendments to an approved action when such
changes would cause no or only minimal environmental
impacts.” 

. The Agencies determined that the “impacts
                                8

[of the Plan] will be beneficial compared to current conditions.”

 (emphasis added). That was because the Plan would
maintain the existing number of flights, currently flying under
interim operating authority, but would reduce their
environmental impacts through the prescribed mitigation
measures. 

     In light of that conclusion, the Agencies finalized the Bay
Area Parks Plan without completing any environmental
assessment or environmental impact statement. Record of
Decision, supra, at 9, 20–21; Record of Decision, supra, app. C
(Categorical Exclusion Documentation Form) at 13–17.

     The Record of Decision for the Plan was a final order of the
FAA, which we have jurisdiction to review. 

(a); 

 § 40128(b)(5).

                               II.

     As the parties argue the case, it centers on whether the
Agencies complied with regulations of the Council on
Environmental Quality, an entity within the Executive Office of
the President. We will not address these arguments. The CEQ
regulations, which purport to govern how all federal agencies
must comply with the National Environmental Policy Act, are
ultra vires.

      CEQ traces its rulemaking authority not to legislation but
to an Executive Order of the President. But “an executive order
is not ‘law’ within the meaning of the Constitution.” California
v. EPA, 

 (2023). The Supreme Court, in one
of its most significant separation of powers decisions, ruled that
the Constitution does not permit the President to seize for
himself the “law-making power of Congress” by issuing an
order that, “like a statute, authorizes a government official to
                                 9

promulgate . . . rules and regulations.” Youngstown Sheet &
Tube Co. v. Sawyer, 

 (1952). The Court
reiterated and emphasized this point in Chrysler Corp. v. Brown,

 (1970): “The legislative power of the United States
is vested in the Congress, and the exercise of quasi-legislative
authority by government departments and agencies must be
rooted in a grant of such power by the Congress and subject to
the limitations which that body imposes.” 

.1

      Yet both sides in this case took for granted CEQ’s authority
to issue binding NEPA regulations. Although questions about
this were raised at oral argument, no party sought leave to file
a post-argument brief. That is understandable. Petitioners
claimed that the Agencies violated CEQ regulations; the
Agencies denied the charge and defended by invoking CEQ
regulations.

      Despite the parties’ acquiescence in CEQ’s regulatory
authority, we “retain[] the independent power to identify and
apply the proper construction of governing law,” and that is
especially true when “the proper construction is that a law does
not govern because it is not in force” or is not legally binding.
U.S. Nat’l Bank v. Indep. Ins. Agents of Am., Inc., 

 (1993) (first excerpt quoting Kamen v. Kemper Fin. Serv.,
Inc., 

 (1991)). Here, CEQ’s authority to issue
regulations on the basis of an Executive Order raises what is
essentially a “separation of powers” issue. Mexichem Fluor,

     1 See,  e.g., Food & Drug Admin. v. Brown & Williamson
Tobacco Corp., 

 (2000) (“[N]o matter how
‘important, conspicuous, and controversial’ the issue, and regardless
of how likely the public is to hold the Executive Branch politically
accountable, . . . an administrative agency’s power to regulate in the
public interest must always be grounded in a valid grant of authority
from Congress.”).
                                10

Inc. v. EPA, 

 (D.C. Cir. 2017) (Kavanaugh,
J.). “To the extent that this structural principle is implicated in
a given case, the parties cannot by consent cure the
constitutional difficulty for the same reason that the parties by
consent cannot confer on federal courts subject-matter
jurisdiction beyond the limitations imposed by Article III . . . .”
Commodity Futures Trading Comm’n v. Schor, 

 (1986); see also Freytag v. Commissioner, 

,
878–89 (1991); Plaut v. Spendthrift Farm, Inc., 

 (1995); Bahlul v. United States, 

, 760 n.1 (D.C.
Cir. 2016) (en banc) (Kavanaugh, J., concurring).

      There are good reasons, indeed there are compelling
reasons, for us to determine the validity of the CEQ regulations
once and for all. Over many years, our court has expressed
serious concerns about whether CEQ’s regulations had any
“binding effect” because it was “far from clear” that CEQ had
any “regulatory authority under [NEPA].” Nevada v. Dep’t of
Energy, 

, 87 n.5 (D.C. Cir. 2006) (quoting TOMAC
v. Norton, 

 (D.C. Cir. 2006); City of
Alexandria v. Slater, 

, 866 n.3 (D.C. Cir. 1999));
see also Grand Canyon Tr. v. FAA, 

, 341 n.* (D.C.
Cir. 2002); Food & Water Watch v. U.S. Dep’t of Agric., 

 (D.C. Cir. 2021) (Randolph, J., concurring). It is
time for our court’s long-standing misgivings to be put to the
test: “where there is so much smoke, there must be a fair amount
of fire, and we would do well to analyze the causes.” Henry J.
Friendly, A Look at the Federal Administrative Agencies, 

, 432 (1960).

                                A.

     The National Environmental Policy Act of 1969 required
each federal agency to issue a “detailed statement” addressing
the environmental impact of any proposed “major Federal
                              11

action[] significantly affecting the quality of the human
environment.” 

(C). All federal agencies were
required to develop procedures implementing NEPA. 

§ 4332(2)(B). NEPA also created a “Council on Environmental
Quality” within the Executive Office of the President, to be run
by three Commissioners appointed by the President and
confirmed by the Senate. Id. § 4342. CEQ’s job was to “review
and appraise” agencies’ compliance with NEPA; to “make
recommendations to the President with respect thereto”; and to
“develop and recommend to the President national policies to
foster and promote the improvement of environmental quality.”
Id. § 4344(3)–(4).

      In 1970, President Nixon issued an Executive Order
instructing CEQ to “[i]ssue guidelines to Federal agencies for
the preparation of” the “detailed statements” NEPA required.
Exec. Order No. 11514, § 3(h), 

, 4248 (Mar.
7, 1970). In response, CEQ published a “memorandum”
containing “guidelines” for federal agencies considering
environmental impact statements. 

, 7724
(Apr. 23, 1971).

      At the time, several courts concluded that CEQ’s role was
“merely advisory” because it lacked any “authority to prescribe
regulations governing compliance with NEPA.” Hiram Clarke
Civic Club, Inc. v. Lynn, 

 (5th Cir. 1973)
(citing Greene Cnty. Planning Bd. v. Fed. Power Comm’n, 

, 421 (2d Cir. 1972)). These courts and others therefore
viewed CEQ’s guidelines as non-binding suggestions to assist
agencies in developing their own NEPA procedures. See
Aertsen v. Landrieu, 

 (1st Cir. 1980); Nat’l
Helium Corp. v. Morton, 

, 656 (10th Cir. 1971).

     CEQ held a quite different view. It considered its
guidelines to be mandatory, “non-discretionary standards for
                               12

agency decision-making.” 

, 55,978 (Nov.
29, 1978). These divergent views were at the center of Sierra
Club v. Morton, 

 (D.C. Cir. 1975). Our court sided
with CEQ, treating its NEPA guidelines as the equivalent of
legally binding rules, entitled to “great respect” and
“heightened” “deference,” and rejected the Department of the
Interior’s environmental impact “statement” (a “statement”
consisting of many thick volumes) because it failed to comply
with those guidelines. 

 at 873 & n. 24.

     When the case reached the Supreme Court, the Solicitor
General—in a quasi-confession of error—advised the Court that
CEQ’s guidelines were not mandatory and “do not bind agencies
of the Executive branch.” Brief for the Petitioners at 31 n.24,
Kleppe v. Sierra Club, 

 (1976) (Nos. 75-552 & 75-
561). As a result, the Supreme Court’s Kleppe v. Sierra Club
opinion, which reversed the D.C. Circuit, made no mention of
CEQ or its guidelines.

      In 1977, President Carter took office and issued Executive
Order 11991, 

 (May 25, 1977), apparently
in response to the Solicitor General’s position in the Kleppe
Supreme Court case. President Carter’s Executive Order was
meant to empower CEQ to issue “regulations,” rather than
“guidelines,” “to Federal agencies for the implementation of the
procedural provisions of [NEPA].” 

 His Executive Order
required all federal agencies to “comply with the regulations
issued by [CEQ]” unless doing so would violate federal law. 

. President Carter imposed these duties “[b]y virtue of”
his authority as President and “in furtherance of the purpose and
policy” of NEPA and several other environmental laws. 

. In so doing, he embarked on “the most ambitious
presidential foray into the nation’s environmental protection
effort: the transformation of the CEQ from an advisory entity
into a regulatory agency.” Scott C. Whitney, The Role of the
                              13

President’s Council on Environmental Quality in the 1990’s and
Beyond, 6 J. Env’t L. & Litig. 81, 84 (1991).

     In compliance with President Carter’s Executive Order,
CEQ issued what amounted to a massive new body of law
“binding on all Federal agencies,” the federal courts, and the
non-federal litigants in NEPA cases and setting forth “uniform
standards applicable throughout the Federal government.” 

,978–79 (Nov. 29, 1978). In its initial foray, CEQ
issued ninety-two NEPA mandatory regulations, many with
numerous subparts containing extensive detailed and intricate
explanations and directives. CEQ’s 1978 regulations replaced
“some seventy different sets of agency regulations,” leaving the
other Executive and independent agencies with only the residual
authority to “issue implementing procedures” for applying
CEQ’s mandates. 

 As authority for its regulations, CEQ
invoked Executive Order 11991 and “the President’s
Constitutional and statutory authority.” 

     Those original CEQ regulations erected a framework that
largely remains in effect to this day. The regulations described
the “detailed statement” NEPA requires for proposed agency
action “significantly affecting the quality of the human
environment.” 

(C); see also 

 (1978). An agency must begin by determining whether
the proposed action would have a significant environmental
effect, and then document its findings in a concise statement
CEQ called an “environmental assessment.” 

 §§ 1501.3–.4,
1508.9. If the agency finds that the action’s environmental
effect would be significant, it must prepare an “environmental
impact statement.” Id. If it does not so find, the agency must
issue a “finding of no significant impact” documenting its
conclusion. See id. § 1508.13.

     CEQ also permitted agencies to comply with NEPA in one
                               14

other way: by invoking what CEQ—coining a phrase—called
a “categorical exclusion.” See id. §§ 1501.4, 1508.4. Under the
regulations, an agency may identify categories of actions that
have no significant environmental effects. Id. If a proposed
action fits into one of those categories, the agency can invoke
the categorical exclusion and avoid preparing an environmental
assessment or an environmental impact statement. Id.2

     In January 2023, the Park Service and the FAA issued a
plan to manage commercial air tours over several national parks
in and around San Francisco. In explaining their environmental
analysis, they repeatedly relied on CEQ’s NEPA regulations.
See J.A. 8–9, J.A. 20–21, 24–25, 58, 151, 159–63. They
asserted that they had complied with NEPA by applying the
Park Service’s categorical exclusion for “[c]hanges or
amendments to an approved action when such changes would
cause no or only minimal environmental impacts.” J.A. 8–9.

                               B.

     Federal agencies, whether executive agencies like the FAA
and the Park Service or independent agencies like the Nuclear
Regulatory Commission and the Federal Energy Regulatory




     2 The National Parks Act contains one provision incorporating

five CEQ regulations dealing mainly with the coordination between
agencies in making NEPA determinations.                

(b)(4)(c). Those regulations are not at issue, and CEQ has
revised them since passage of the National Parks Act in 2020 and
2024. Noticeably absent even from the National Parks Act’s
incorporation is CEQ’s regulation dealing with “categorical
exclusion,” which is at issue in this case.
                                15

Commission,3 are creatures of statute and as such “literally
ha[ve] no power to act” except to the extent Congress authorized
them. FEC v. Ted Cruz for Senate, 

, 301 (2022)
(quoting La. Pub. Serv. Comm’n v. FCC, 

(1986)). For CEQ’s regulations to be legally binding on
agencies, courts, and the public, “it is necessary to establish a
nexus between the regulations and some delegation of the
requisite legislative authority by Congress.” Chrysler, 

. Then-Judge Kavanaugh put it this way: “The separation
of powers and statutory interpretation issue that arises again and
again in this Court is whether an executive or independent
agency has statutory authority from Congress to issue a
particular regulation.” Mexichem, 

.

     The “separation of powers and statutory interpretation
issue” that CEQ’s regulations present is thus unremarkable.
What is quite remarkable is that this issue has remained largely
undetected and undecided for so many years in so many cases.

      One apparent reason for the oversight is that CEQ
publishes its “regulations” in the Code of Federal Regulations,
as if that were a credential. The temptation for litigants and
courts is to treat publication in the C.F.R. as equal to publication
in the United States Code. Trouble is that publication in the
C.F.R. is no measure of an agency’s authority to issue rules that
appear there, as Professor Merrill has explained. Thomas W.
Merrill, Judge Williams on Administrative Law, 16 N.Y.U. J. L.
& Liberty 98, 100–02 (2022) (discussing Health Ins. Ass’n v.
Shalala, 

 (D.C. Cir. 1994)). The provisions of

     3 The Federal Energy Regulatory Commission is a five-member

“independent regulatory commission” within the Department of
Energy. 

(a). Both it and the Nuclear Regulatory
Commission are considered independent agencies pursuant to 

(5).
                                 16

NEPA provide no support for CEQ’s authority to issue binding
regulations. No statutory language states or suggests that
Congress empowered CEQ to issue rules binding on other
agencies—that is, to act as a regulatory agency rather than as an
advisory agency.4 NEPA contains nothing close to the sort of
clear language Congress typically uses to confer rulemaking
authority. See Thomas W. Merrill & Kathryn Tongue Watts,
Agency Rules with the Force of Law: The Original Convention,

, 471–76 (2002).

     No statute confers rulemaking authority on CEQ. President
Carter’s Executive Order cited section 309 of the Clean Air Act.

 (May 25, 1977). Under this provision, the
Administrator of the Environmental Protection Agency reviews
the environmental impact of other federal agencies’ proposed
actions. 

(a). If the EPA Administrator finds
that the proposed action is “unsatisfactory” from an
environmental-quality standpoint, he must “publish his
determination” and refer the matter to CEQ. 

 § 7609(b). That
provision is consistent with CEQ’s advisory role; it says nothing
about CEQ’s rulemaking authority. The Executive Order also
cites the Environmental Quality Improvement Act of 1970,
which established an Office of Environmental Quality headed


     4 The legal status of the Council of Economic Advisors, another

entity in the Executive Office of the President, provides an example
and a contrast. As our court observed, the duties Congress assigned
to the Council of Economic Advisors “are, for all practical purposes,
identical” to the duties Congress assigned to CEQ. Rushforth v.
Council of Econ. Advisers, 

, 1041–42 (D.C. Cir. 1985)
(citing 

(c)). Unlike CEQ, no Executive Orders
“expanded” the powers of the Council of Economic Advisors and it
has remained exactly where Congress initially put it: in “the realm of
entities the sole function of which is to advise and assist the
President.” 

                                 17

by the chairman of CEQ. 

(a). Even as the
director of that Office, however, CEQ’s chairman only has the
authority to “assist[]” other federal agencies. 

 § 4372(d)(2),
(5), (6). The Chairman may “promulgate regulations” but only
related to a fund used to finance the Office’s projects and
research studies.5 Id. § 4375.

      The Supreme Court’s pronouncements in this area cannot
rescue CEQ’s regulations. The Court once wrote that CEQ’s
regulations under NEPA are “entitled to substantial deference.”
Andrus v. Sierra Club, 

 (1979). But that
Chevron-like statement did not result from an examination of
CEQ’s authority to issue judicially enforceable regulations and
cannot be credited in light of the Supreme Court’s ruling in
Loper Bright Enterprises v. Raimondo, 

 (2024).
In another case, the Supreme Court stated that CEQ was
“established by NEPA with authority to issue regulations
interpreting it.” Pub. Citizen, 541 U.S. at 757. The statement
appeared without any accompanying legal analysis. We must
obey “carefully considered language of the Supreme Court, even
if technically dictum.” Winslow v. FERC, 

(D.C. Cir. 2009) (quoting United States v. Dorcely, 

 (D.C. Cir. 2006)). But we are not bound by every stray
remark on an issue the parties neither raised nor discussed in any
meaningful way. See Webster v. Fall, 

 (1925);
Cohens v. Virginia, 

, 399–400 (1821)
(Marshall, C.J.).


     5 Also worth mentioning is the “housekeeping statute,” 

, which empowers “the head of an Executive department” to
“prescribe regulations for” the governance of his department and its
operations. This is “simply a grant of authority to the agency to
regulate its own affairs” and internal functions. Chrysler, 

.
                                 18


      The CEQ regulations are by no means a mere delegation of
the President’s authority under the Take Care Clause. See U.S.
Const. art. II, § 3; 

; see also Whitney, supra, at
91.     Executive Orders focused solely on the internal
management of the Executive Branch create no private rights
and are not judicially reviewable. California v. EPA, 

. NEPA, by contrast, “imposes statutory obligations that
agencies must execute consistent with the requirements of the
APA,” and affect private parties who may seek judicial review
of agencies’ compliance. 

 (citing Cmtys. Against Runway
Expansion, Inc. v. FAA, 

 (D.C. Cir. 2004)).6
If all federal agencies are bound by the CEQ regulations and
must follow them in carrying out their obligations under NEPA,
and if the regulations are enforceable by courts, then those
regulations cannot be justified solely as an exercise in a
President’s oversight of his Administration.

     Besides, upholding the CEQ regulations on the theory that
these amount to Presidential oversight would raise additional
problems. The regulations “replace[d]” the rules of some
seventy federal agencies, 43 Fed. Reg. at 55,978, and limited the
agencies’ role to supplementing CEQ’s work with
“implementing procedures,” 

(a) (1978).
Once the CEQ rules went into effect, they served as binding
regulations across the whole of government. And yet Supreme
Court decisions hold that the Take Care Clause cannot be used
to bypass agencies’ limited status as “creatures of statute,”

     6 See Pub. Citizen, 541 U.S. at 768 (“The informational role of

an [environmental impact statement] is to give the public the assurance
that the agency has indeed considered environmental concerns in its
decisionmaking process, and, perhaps more significantly, provide a
springboard for public comment in the agency decisionmaking process
itself.”).
                                  19

“possess[ing] only the authority that Congress has provided
them.” Nat’l Fed’n of Indep. Bus. v. OSHA, 

(2022). To repeat, the Constitution does not permit the
President to seize for himself the “law-making power of
Congress” by issuing an order that, “like a statute, authorizes a
government official to promulgate . . . rules and regulations.”
Youngstown, 

 (1952); see also Whitney, supra,
at 92–94.7


     7 See NLRB v. Noel Canning, 

, 571–72 (2014)
(Scalia, J., joined by Roberts, C.J., Thomas & Alito, J.J., concurring
in the judgment):

                 “[W]hen questions involving the
        Constitution’s government-structuring provisions are
        presented in a justiciable case, it is the solemn
        responsibility of the Judicial Branch ‘to say what the
        law is.’ Zivotofsky v. Clinton, 

        (2012) (quoting Marbury v. Madison, 

 (1803)). This Court does not defer to the other
        branches resolution of such controversies; as Justice
        KENNEDY has previously written, our role is in no
        way “lessened” because it might be said that “the two
        political branches are adjusting their own powers
        between themselves.” Clinton [v. City of New York,
        

 (1998)] (concurring opinion).
        Since the separation of powers exists for the
        protection of individual liberty, its vitality “does not
        depend” on “whether ‘the encroached-upon branch
        approves the encroachment.’ ” Free Enterprise Fund,
        

, 497 2010)(quoting New York v. United
        States, 

 (1992)); see also Freytag
        v. Commissioner, 

, 879–880 (1991);
        Metropolitan Washington Airports Authority v.
        Citizens for Abatement of Aircraft Noise, Inc., 

, 276–277 (1991). Rather, policing the
        “enduring structure” of constitutional government
                                  20

     CEQ therefore had no lawful authority to promulgate these
regulations. One wrinkle remains. Many agencies, including
the parent departments of the agencies here (the Department of
the Interior, for the Park Service, and the Department of
Transportation, for the FAA), have issued their own NEPA
regulations. If an agency adopts CEQ’s rules or incorporates
them by reference into its NEPA regulations, would that be a
permissible exercise of its own rulemaking authority?8 The
question is a good one, but it does not describe this case.

      CEQ’s regulations, as mentioned, instruct agencies to
“confine themselves” to issuing only “implementing
procedures” that “comply with [CEQ’s] regulations.” 

(a)–(b) (1978). The implementing procedures “shall
not paraphrase” CEQ’s rules. 

 So the CEQ regulations
represent the framework for all agencies’ compliance with
NEPA, leaving the agencies to fill in certain details specific to
their programs.

     As a result, the Agencies here have neither adopted the
content of the CEQ regulations nor incorporated those rules by
reference. Instead, they obeyed CEQ’s command and accepted
the CEQ regulations as a stand-alone body of law that they must


        when the political branches fail to do so is “one of the
        most vital functions of this Court.” Public Citizen v.
        Department of Justice, 

 (1989)
        (KENNEDY, J., concurring in judgment).”
     8 This court has explained in other contexts that an agency

cannot outsource authority over the content of its regulations to an
entity that itself lacks rulemaking authority. See Ass’n of Am. R.R.s.
v. U.S. Dep’t of Transp., 

, 670–71 (D.C. Cir. 2013),
vacated & remanded on other grounds, 

 (2015); NRDC v.
EPA, 

, 8–9 (D.C. Cir. 2006).
                               21

obey and the courts must enforce. The Department of the
Interior’s NEPA rules, for example, are meant to be used “for
compliance with” the CEQ regulations. 

(a)(2).
Interior’s regulations “supplement, and [are] to be used in
conjunction with, the CEQ regulations.” 

 § 46.20(a). And
although the Department of the Interior once stated that it was
“incorporat[ing]” certain CEQ guidance documents, it never said
the same of the regulations. 

, 61,292,
61,298 (Oct. 15, 2008). The Department of Transportation’s
rules are similar: they are “not a substitute for” the CEQ
regulations; do not “repeat or paraphrase the language of those
regulations”; and merely “supplement[] the CEQ regulations by
applying them to DOT programs.” Dep’t of Transp., Order
5610.1C, at 2 (July 30, 1985).

      The Agencies’ NEPA analysis in this case reflected that
reality. They repeatedly invoked the CEQ regulations, not their
own rules, as the source of the overarching regulatory
framework they applied. See J.A. 8–9, 20–21, 24–25, 58, 151,
159–63. Their own NEPA regulations came up only to deal
with certain agency-specific aspects of the analysis. See J.A. 9,
20, 161, 169–73, 192, 194, 204–05, 220.

     Even if Interior and Transportation had incorporated CEQ’s
regulations as their own, they would have been able to do so
only for the original 1978 version of the CEQ’s rules. Interior’s
current rules went into effect in 2007; Transportation’s in 1985.
The CEQ regulations were revised twice before 2023, when the
Agencies formulated the Plan. See 

 (May
20, 2022); 

 (July 16, 2020). See Wild Va. v.
Council on Env’t Quality, 

 (4th Cir. 2022).
The Agencies could not have adopted a body of rules that did
not exist at the time. Even if that were possible, nothing in the
                                22

agencies’ rules evinced an intent to automatically incorporate
every new iteration of the CEQ regulations.9

                               III.

                                A.

      Petitioners, without invoking CEQ regulations, argue that the
Agencies relied on an improper baseline for their environmental
analysis by using the existing level of flights under interim
operating authority as the baseline for assessing the
environmental effects of the Plan. We agree and hold that it was
arbitrary and capricious for the Agencies to treat interim
operating authority as the status quo for their NEPA analysis.
We reject or decline to reach the rest of Petitioners’ arguments.

      When conducting an environmental analysis of a proposed
action under NEPA, an agency compares the action’s projected
environmental effects to the existing condition of the
environment. Through that comparison, the agency can
ascertain the magnitude of the proposed action’s environmental
impacts. The agency’s choice of the baseline for comparison
matters a great deal. If the baseline is artificially high, the
agency might erroneously conclude that even highly disruptive
actions will have minimal incremental environmental effects. In
that event, the agency might avoid conducting a more
comprehensive environmental analysis required by NEPA.

     In preparing the Bay Area Parks Plan, the Agencies treated
the existing air tours in the Parks as the status quo for purposes

     9 It is worth considering whether, under the Administrative

Procedure Act, each agency would be required to hold a separate
notice and comment rulemaking proceeding before incorporating by
reference any CEQ regulatory amendments.
                              23

of conducting their NEPA analysis. Those tours were conducted
under interim operating authority. With the thousands of air
tours conducted pursuant to interim operating authority serving
as the baseline for comparison, the Agencies concluded that the
Plan would have “no or minimal” environmental impacts.
Record of Decision, supra, at 8–9. But by treating interim
operating authority as the baseline, the Agencies enshrined
the status quo without evaluating the environmental impacts
of the existing flights. That outcome stands at odds with the
Agencies’ duties under the Act and NEPA.

     Under the Act, “[t]he objective of any air tour management
plan shall be to develop acceptable and effective measures to
mitigate or prevent the significant adverse impacts, if any, of
commercial air tour operations upon the natural and cultural
resources, visitor experiences, and tribal lands.” 

(b)(1)(B). The Act thereby confers a duty upon the
Agencies to develop “acceptable and effective” Plans that
“mitigate or prevent” significant environmental harms. The
Agencies cannot sidestep those obligations by tilting the scales
in a way that obscures the true environmental effects of a Plan.

      That, though, is effectively what the Agencies have done
here. The Agencies “decided to implement the existing
condition”—that is, existing tours conducted under interim
operating authority—in the Plan “because the impacts
associated with the existing condition, together with reasonable
mitigation measures included in the Plan, would not result in
significant adverse impacts of commercial air tour operations
upon the natural and cultural resources of any of the Parks or
visitor experience in any of the Parks.” Record of Decision,
supra, at 14. But the “the impacts associated with the existing
condition” along with the “mitigation measures” in the Plan
would “not result in significant adverse impacts” only because
they were compared to the existing condition itself. It was
                               24

unreasonable for the Agencies to avoid fully treating the
environmental effects of the Bay Area Parks Plan on the ground
that those effects would minimally alter a status quo that itself
has never been adequately assessed. See id. at 21 (“The
agencies acknowledge that no previous NEPA analysis of
[interim operating authority] occurred. ”).

      The Agencies insist that Congress set interim operating
authority as the status quo and that their choice of interim
operating authority as the baseline thus was reasonable. True,
Congress provided for granting interim operating authority as a
means of smoothing the transition between the pre- and post-Air
Tour Management Act worlds. But Congress did not intend for
the Agencies to treat the level of pre-Act air tours as a legal
status quo against which to compare all potential Plans. Under
such an approach, the Agencies could grandfather in all pre-Act
air tours without ever conducting a NEPA analysis. Congress,
though, enacted the Act to “preserve, protect, and enhance the
environment by minimizing, mitigating, or preventing the
adverse effects of aircraft overflights” on national parks. 

(2), 114 Stat. at 186.

      To achieve those objectives, Congress constructed a
detailed scheme by which any operator of national-park air tours
would be required to obtain approval from the Agencies, and the
Agencies would likewise be required to develop detailed plans
governing commercial air tour operations. See 

(b). While that process plays itself out, existing
operators can continue conducting flights pursuant to interim
operating authority, but that authority can be revoked at any
time for cause and it automatically expires six months after
establishment of a Plan. 

 § 40128(c)(2)(D)–(E). Interim
operating authority thus was always meant to be interim—that
is, temporary. Indeed, the Agencies themselves describe interim
operating authority as a “stopgap measure.” Record of Decision,
                               25

supra, at 23. But by treating interim operating authority as the
baseline for assessment of a Plan, the Agencies effectively
transform a stopgap into a permanent part of a Plan that never
undergoes NEPA analysis.

      This case is unlike Conservation Law Foundation v. FERC,

 (D.C. Cir. 2000), on which the Agencies rely.
There, we upheld the Federal Energy Regulatory Commission’s
decision to use the existing conditions of an operating dam as
the baseline for analyzing the environmental effects of
relicensing the dam. But we noted that the relevant statute “says
nothing about whether the baseline for the Commission’s
comparative inquiry should be today or sometime other than
today.” 

. By contrast, the Parks Act makes clear that
the provisional grant of interim operating authority should not
function as the baseline for environmental analysis. In addition,
we noted in Conservation Law Foundation that, regardless of
the Commission’s choice of baseline, it had “fully examined”
the environmental effects of its proposed action and the
alternative options. 

 Here, however, the Agencies failed to
fully consider the Plan’s environmental effects because they
treated the effects of the existing flights as a starting point.

      For these reasons, we hold that the Agencies acted
arbitrarily by using the air tours conducted under interim
operating authority as the baseline for evaluating the Bay Area
Parks Plan’s environmental effects. Because we hold that the
Agencies measured environmental impacts against an improper
baseline, we need not consider Petitioners’ argument that the
Agencies erred by excluding 2015–2016 flight data from that
baseline. Nor need we address their contention that interim
operating authority does not qualify as an “approved action” for
purposes of the approved-action categorical exclusion.
                                26


                                B.

     Petitioners argue that the Agencies’ decision not to prepare
an environmental assessment or environmental impact statement
was arbitrary for two additional reasons: (i) the Agencies had
previously decided to prepare an environmental assessment for
the Bay Area Parks and abandoned that plan, and (ii) the
Agencies have prepared—or are planning to prepare
—environmental assessments for other, allegedly similar
national parks. We reject both arguments.

     First, it was not arbitrary for the Agencies to reverse course
and decline to prepare an environmental assessment for the Bay
Area Parks. In 2011, the Agencies published a notice in the
Federal Register stating their intent to prepare an environmental
assessment for the Parks. See 76 Fed. Reg. at 45,312. The
Agencies “paused” that process upon amendment of the Act in
2012 and later “formally terminated” the process in 2020. Record
of Decision, supra, at 2–3. When an agency reverses course, it
must “display awareness that it is changing position” and “show
that there are good reasons for the new policy.” FCC v. Fox
Television Stations, Inc., 

 (2009) (emphasis
omitted). Here, the Agencies acknowledged their change of
course and provided a reasonable explanation for it: to initiate
fresh environmental review processes better suited to current
circumstances. See 85 Fed. Reg. at 55,060; accord Record of
Decision, supra, at 4.

    Second, it was not arbitrary for the Agencies to decline to
prepare an environmental assessment for the Bay Area Parks
even though they prepared or are planning to prepare
environmental assessments for purportedly similar national
parks. Petitioners’ argument boils down to a simplistic
comparison between the number of air tours conducted in the
Bay Area Parks and the number of air tours conducted
                                27

elsewhere. But the Agencies must consider a slew of factors in
addition to the absolute number of air tours. Those factors
include air tour routes, the altitudes for those tours, restrictions
for particular events, noise consequences, and visual impacts.
See 

(b)(3)(B). And the Agencies must
consider the effects upon the “natural and cultural resources”
and “visitor experiences” of the relevant park. 

§ 40128(b)(1)(B). The Agencies are therefore tasked with
conducting a highly park-specific inquiry involving far more
than simply counting the number of air tours. We extend
agencies considerable discretion to weigh an open-ended set of
factors, see Nat’l Wildlife Fed’n v. EPA, 

, 570
(D.C. Cir. 2002), especially when the agency must make a
“predictive judgment regarding a matter within its sphere of
expertise,” Fresno Mobile Radio, Inc. v. FCC, 

 (D.C. Cir. 1999). In that light, we decline to second-guess
the Agencies’ decision not to prepare an environmental
assessment for the Bay Area Parks solely because they prepared
environmental assessments for other parks.

                                IV.

      We come then to the question of remedy. Pursuant to
section 706(2) of the Administrative Procedure Act, 

(2), a reviewing court “shall . . . hold unlawful and set
aside” agency action that violates the APA. Our precedents
have authorized remand without vacatur but “only if an agency’s
error is ‘curable.’” Bridgeport Hosp. v. Becerra, No. 22-5249,
--- F.4th ----, 

, at *7 (D.C. Cir. July 23, 2024)
(quoting U.S. Sugar Corp. v. EPA, 

 (D.C. Cir.
2016)). As discussed in Part III above, the Agencies’ actions
were ultra vires when they determined that their Plan would
have no environmental impact as compared with the existing
tour flights permitted on an interim basis. The Agencies will
now need to take a completely different tack to complete their
                               28

NEPA review. Because the Agencies have not shown “at least
a serious possibility” that they will be able to reach the same
outcome on remand, we must vacate the Plan. 

 (quoting
Allied-Signal, Inc. v. U.S. Nuclear Regul. Comm’n, 

, 151 (D.C. Cir. 1993)).

      If the Agencies and Petitioners desire to keep the current
Plan in place while the Agencies restart their NEPA review, the
parties may move for a stay of our mandate. Honeywell Int’l
Inc. v. EPA, 

, 1375 (D.C. Cir. 2004) (Randolph,
J., concurring); accord Griffin v. HM Fla.-ORL, LLC, 

, 2 n.1 (2023) (statement of Kavanaugh, J.). This approach has
several practical advantages. It allows the court to hear from
both sides, and perhaps from intervenors or amici curiae, gather
information about the consequences of granting or denying
relief, and decide the question in accordance with our well-
established standards for issuing a stay. See NRDC v. EPA, 

, 1263–64 (D.C. Cir. 2007) (Randolph, J., concurring).

     A stay can also place limits and reporting requirements on
an agency, thus giving “the agency an incentive to act in a
reasonable time.” 

 (Randolph, J., concurring). One
might expect that the Agencies will move “promptly” on
remand. But an expectation is not an obligation. This court has
already had to issue a writ of mandamus to force the Agencies’
hands. See In re PEER, 

. Petitioners should not
be saddled with having to clear the bar of mandamus relief if the
Agencies take too long. The Agencies acted without authority;
they should bear the burden of justifying a stay of the mandate.
                              * * *

     The petition for review is granted, the FAA’s order is
vacated, and the case is remanded to the FAA.

                                                     So ordered.
    RANDOLPH, Senior Circuit Judge, concurring with respect
to Part IV:

     As I have maintained, the Administrative Procedure Act
requires courts to vacate agency action determined to be
unlawful. See Checkosky v. SEC, 

 (D.C. Cir.
1994) (opinion of Randolph, J.); NRDC v. EPA, 

 (D.C. Cir. 2007) (Randolph, J., concurring); Comcast
Corp. v. FCC, 

 (D.C. Cir. 2009) (Randolph, J.,
concurring). Section 706(2) provides that a reviewing court
“shall . . . hold unlawful and set aside” agency action that
violates the APA. 

(2). “Shall” in § 706 conveys
a “command,” as it does in ordinary usage. Loper Bright Enters.
v. Raimondo, 

, 2265 (2024). And to “set aside”
is to vacate, as confirmed by the text, the structure, and the
history of the APA, and the longstanding practices of this court
and the Supreme Court—all of which Justice Kavanaugh proved
conclusively in Corner Post, Inc. v. Board of Governors of the
Federal Reserve System, 

, 2462–64 (2024)
(Kavanaugh, J., concurring).

     Section 706(2)’s text thus admits of only one meaning: a
court must—not may—vacate agency action that is arbitrary or
capricious or otherwise unlawful. A long line of this court’s
precedents reinforce that conclusion. See Comcast, 579 F.3d at
10–11 & n.2 (Randolph, J., concurring) (collecting cases);
Checkosky, 23 F.3d at 491–93 & n.35 (opinion of Randolph, J.)
(same). It is true that there are decisions of this court ordering
remand without vacatur. E.g. Allied-Signal, Inc. v. U.S. Nuclear
Regul. Comm’n, 

, 151 (D.C. Cir. 1993). But not
one of those decisions even attempted to explain how “shall”
and “set aside” in § 706(2) could possibly mean
“disregard” and “keep in place” unlawful agency action. See
Webster v. Fall, 

 (1925).
                               2

     Internal deliberations of the Supreme Court in Bowen v.
Georgetown University Hospital, 

 (1988),
unearthed with the release of the Thurgood Marshall papers,
support this view. See Ronald M. Levin, “Vacation” at Sea:
Judicial Remedies and Equitable Discretion in Administrative
Law, 

, 351--52 (2003). Justice Kennedy’s draft
opinion had initially stated that a reviewing court could remand
an illegal rule without vacating it. 

 Justice Kennedy deleted
that portion of his draft after Justice Scalia circulated a
memorandum with which several other justices agreed. 

Justice Scalia’s memorandum first quoted § 706(2) with
particular emphasis on the word “shall” preceding “set aside,”
and then said this:
    I think it would be buying grief to suggest that a court
    may exercise its equitable discretion to disregard [§
    706(2)] by leaving a regulation “not in accordance with
    law” in effect, or by allowing a revised rule to be
    formulated and then applied as though it had been
    issued earlier. For one thing, since not all proceedings
    calling a rule into question are equitable proceedings –
    for example, a civil penalty suit brought by the agency
    for violation of the invalid rule – such a principle
    would create considerable potential for inconsistent
    application. (The ordinary statutory provision for
    direct court-of-appeals review of rulemaking does not,
    I think, establish an equitable proceeding . . . .) Even
    apart from this problem, however, I am sure it is not
    wise for us to invite agencies to seek exercise of
    ‘equitable discretion’ to let invalid rules stand.
    Id. Thus, § 706(2) forecloses judicial discretion, equitable
or otherwise. See Miller v. French, 

, 340–341
(2000).
     SRINIVASAN, Chief Judge, dissenting with respect to Parts
II and IV:

     I join Part III of the court’s opinion, in which we reject the
Agencies’ use of the existing level of flights under interim
operating authority as the baseline for measuring the
environmental effects of their Air Travel Management Plan.
Respectfully, though, I am unable to join Parts II and IV of the
court’s opinion, in which my colleagues, respectively: (i)
consider whether the CEQ has authority to issue binding NEPA
regulations and conclude it does not; and (ii) determine that the
Agencies’ challenged action must be vacated even though the
effect of vacatur is to put the prevailing party (petitioners) in a
worse position. No party in this case asks us take either of
those steps. And in substantially similar circumstances, our
court has consistently refrained from unnecessarily deciding
the CEQ regulations’ validity or unnecessarily vacating agency
action. I would follow the same course here.

     1. In Part II of the court’s opinion, my colleagues
determine that the CEQ lacks authority to issue binding
regulations implementing NEPA. There is no cause to reach
that issue in this case.

     First and foremost, no party challenges the CEQ’s
regulations. In nonetheless reaching out to address the issue,
the court contravenes “our established ‘principle of party
presentation.’” Keepseagle v. Perdue, 

(D.C. Cir. 2017). That principle embodies the idea “that
appellate courts do not sit as self-directed boards of legal
inquiry and research, but essentially as arbiters of legal
questions presented and argued by the parties before them.”
McBride v. Merrell Dow & Pharm., 

 (D.C.
Cir. 1986). After all, “[o]ur adversary system is designed
around the premise that the parties know what is best for them,
and are responsible for advancing the facts and arguments
entitling them to relief.” Castro v. United States, 

,
                                2
386 (2003) (Scalia, J., concurring in part and concurring in
judgment). And when no party raises an issue, we of course
lack the benefit of the parties’ presentation of briefing and
argument on it.

     Of particular salience, we have specifically and steadfastly
adhered to the party presentation principle in declining to
address the exact issue my colleagues venture out to decide
today. Time and again, we have refrained from questioning the
CEQ’s authority to adopt binding NEPA regulations because
the parties did not raise the challenge. See, e.g., Nevada v.
Dep’t of Energy, 

, 87 n.5 (D.C. Cir. 2006) (“The
DOE accepts [the CEQ regulations] as binding, as do we for
purposes of this appeal.”); Grand Canyon Tr. v. FAA, 

, 341 n.* (D.C. Cir. 2002) (“Neither party challenges the
regulatory authority of the CEQ, and hence we have no
occasion to question the binding effect of the regulations on the
FAA.”); City of Alexandria v. Slater, 

, 866 n.3
(D.C. Cir. 1999) (“Because the Administration does not
challenge the Council's regulatory authority, we treat the
Council's regulations as binding on the agency.”).

     There is all the more reason to abide by the party
presentation principle in this case because we are already ruling
in favor of the petitioners on another ground they did raise: that
the Agencies’ choice to use the existing level of flights as the
baseline was improper. The relevant CEQ regulation enables
the Agencies to rely on a “categorical exclusion” from NEPA’s
otherwise-applicable requirement to prepare a formal
environmental analysis. See 

(a)(1), 1501.4
(2020); Maj. Op. 12, supra. Petitioners do not challenge the
validity of the categorical-exclusion regulation, but instead
argue (among other things) that the Agencies’ reliance on the
regulation was improper because it rested on an improper
baseline. The court today agrees with petitioners on that score.
                               3
And because we hold that the Agencies’ reliance on the
categorical-exclusion regulation was improper, there is no need
to consider whether the regulation is valid—even aside from
the fact that no one is challenging the regulation’s lawfulness
in the first place.

     My colleagues ground their decision to assess the CEQ’s
authority to issue binding regulations on the idea that the
question implicates the separation of powers. See Maj. Op. 8,
supra. But that of course was no less true in the repeated
occasions in which we declined to address precisely the same
issue because no party raised the challenge. Even if the parties
could not “by consent cure” the issue if it were squarely
presented, id. (quoting Commodity Futures Trading Comm’n v.
Schor, 

 (1986)), my colleagues do not
suggest that the court is somehow obligated to address the issue
even though no party has presented it. Rather, as our consistent
line of decisions declining to address the validity of the CEQ
regulations confirms, the normal rule that we do not take up a
challenge unless a party raises it is fully applicable here.

     Even assuming the party presentation principle could give
way in certain circumstances involving a separation-of-powers
issue, this case would not be a prime candidate for that kind of
exception. My colleagues reference Mexichem Fluor, Inc. v.
EPA, 

 (D.C. Cir. 2017), in support of their
invocation of separation-of-powers principles as a reason to
address the CEQ regulations’ validity. Maj. Op. 8, 13, supra.
Unlike in this case, the party in Mexichem raised the issue the
court decided—whether EPA had authority to issue a rule
restricting the manufacture of products containing a regulated
chemical. 

. The restrictive effect of the
challenged rule fell directly on a regulated private party, a
context in which we are generally sensitive to the “bedrock
separation of powers principle[]” of assuring the agency’s
                               4
authority to impose the regulatory burden. Id.; cf. Seila Law
LLC v. CFPB, 

, 223 (2020) (“The Framers
recognized that, in the long term, structural protections against
abuse of power were critical to preserving liberty.”) (quoting
Bowsher v. Synar, 

 (1986)).

     Here, by contrast, the CEQ’s relevant regulation operates
directly on the Agencies, not on a regulated private party: the
regulation enables the Agencies to forgo preparing a formal
environmental analysis if a categorical exclusion is available.
And by doing so, the regulation enables the Agencies to
circumscribe their regulatory ambit, not expand it. What is
more, to the extent my colleagues believe the party presentation
principle should give way even if the party bound by a CEQ
regulation is an agency rather than a regulated party, the
regulation in question here does not in fact bind an agency.
Instead, the regulation enables an agency to rely on a
categorical exclusion without requiring the agency to do so.
See 

 (2020). Whatever interest there may
be in determining the CEQ’s authority to issue binding NEPA
regulations, that interest is diminished in a case that does not
involve a regulation that in fact binds.

    For all of those reasons, I would adhere to our consistent
practice of declining to address the validity of the CEQ
regulations when no party asks us to do so.

     2. My colleagues not only address an issue that no party
raises, but they also order a remedy that no party desires. That
action, too, is out of step with our decisions in like
circumstances.

    Petitioners, the prevailing parties in this case,
understandably do not want a vacatur of the Agencies’ Air
Travel Management Plan.       That remedy would leave
                               5
petitioners worse off than the status quo. A vacatur of the
Agencies’ Plan would reinstate the pre-Plan regime—that is,
the level of flights permitted under the interim operating
authority but without the mitigating environmental measures
instituted by the Plan. Vacatur, then, “would at least
temporarily defeat . . . the enhanced protection of the
environmental values” at stake. Ctr. for Biological Diversity v.
EPA, 

 (D.C. Cir. 2017) (alteration in original)
(quoting North Carolina v. EPA, 

, 1178 (D.C.
Cir. 2008) (per curiam)).

     Largely for that reason, “[n]o party to this litigation asks
that the court vacate [the Plan].” Env’t Def. Fund v. Adm’r,
U.S. EPA, 

, 190 (D.C. Cir. 1990). Petitioners,
while successfully challenging the Plan, submit that vacatur
would be “unjust” because it would only increase air tours’
environmental effects on the Bay Area Parks. Pet. Reply Br.
26. The Agencies, for their part, agree. While they defend the
Plan, they allow that if petitioners’ challenge succeeds, then
“vacating the Plan while the Agencies conducted more
environmental analysis would cause disruptive consequences.”
Agencies’ Br. 67. And because “the adverse consequences
would fall on the very places and people that the Plan protects,”
the Agencies explain, “the Court should exercise its equitable
discretion by leaving the Plan in place while the Agencies
conduct more NEPA analysis.” Id. at 68.

    When confronted with similar circumstances, our court
has repeatedly remanded to an agency without vacating a
flawed but environmentally protective agency action. See, e.g.,
Ctr. for Biological Diversity, 861 F.3d at 188–89; North
Carolina, 550 F.3d at 1178; Env’t Def. Fund, 898 F.2d at 190;
Sierra Club v. EPA, 

 (D.C. Cir. 1999); Nat’l
Lime Ass’n v. EPA, 

 (D.C. Cir. 2000); U.S.
Sugar Corp. v. EPA, 

 (D.C. Cir. 2016) (per
                                6
curiam); Am. Fuel & Petrochemical Mfrs. v. EPA, 

 (D.C. Cir. 2019 (per curiam). I see no reason to do
otherwise here.

     My colleagues express uncertainty about whether the
Agencies would ultimately be able to achieve the same result
as the successfully-challenged Plan. Maj. Op. 24, supra. The
question, though, is what happens while the Agencies
undertake that analysis. And in that regard, there is no cause
here for putting the prevailing party in a worse position than
the status quo while the proceedings before the Agencies move
forward. To the contrary, “[w]e have [] frequently remanded
without vacating when a rule’s defects are curable and where
vacatur would at least temporarily defeat . . . the enhanced
protection of the environmental values covered by the [rule].”
U.S. Sugar Corp., 

 (emphasis added) (quotation
marks and citation omitted). The defect here—the Agencies’
use of an improper baseline—is at least “curable.” 

     In North Carolina v. EPA, for instance, we determined that
the Clean Air Interstate Rule (CAIR) was “fundamentally
flawed” and that “[n]o amount of tinkering with the rule or
revising of the explanations will transform CAIR, as written,
into an acceptable rule.” 

, 929–30 (D.C. Cir.
2008). But we remanded without vacatur, explaining that,
“notwithstanding the relative flaws of CAIR, allowing CAIR
to remain in effect until it is replaced by a rule consistent with
our opinion would at least temporarily preserve the
environmental values covered by CAIR.” 550 F.3d at 1178.
We described that “method of disposition [as] consistent with
the court’s precedents.” Id.

    Along the same lines, in Sierra Club v. EPA, we rejected
EPA’s methodology in a rule as “hopelessly irrational.” 

. But we remanded without vacatur because Sierra
                               7
Club “expressly requested that we leave the current regulations
in place during any remand, rather than eliminate any federal
control at all.” 

 We found it adequate that “[i]t is possible
that EPA may be able to explain” its approach. Id.; see, e.g.,
Nat’l Lime Ass’n, 

 (“In view of [the petitioner’s]
request that we not vacate the EPA’s regulations, because to do
so would at least temporarily defeat [its] purpose, the enhanced
protection of the environment, we will leave the current []
regulations in place during remand.”) (internal quotation marks
and citation omitted); Env’t Def. Fund, 898 F.2d at 190
(remanding without vacatur because “[n]o party to this
litigation asks that the court vacate the EPA’s regulations, and
to do so would at least temporarily defeat petitioner’s purpose,
the enhanced protection of the environmental values covered
by the [regulations]”). I would apply the same approach—and
reach the same conclusion—in this case.