Griffith, Circuit Judge An arbitration panel determined that the Republic of Argentina was liable to AWG Group Ltd. for $20 million. Argentina challenged that decision in district court, arguing that a member of the arbitration panel had, with a connection to two of the parties to the proceeding, shown "evident partiality" under 9 U.S.C. § 10 (a)(2), and that the way the panel reached its determination exceeded its authority under § 10(a)(4). The district court enforced the panel's award against Argentina, and we affirm.

I

In 1993, Argentina awarded a contract to Aguas Argentinas S.A. (AASA), a consortium of seven companies. Three were Argentine and four were not (AWG Group Ltd. ("AWG"), Sociedad General de Aguas de Barcelona S.A., Vivendi Universal, S.A. ("Vivendi"), and Suez). According to the contract, AASA agreed to invest in and operate Argentina's water services. By its terms, the contract was set to run through 2023 but allowed for earlier termination if either AASA or Argentina failed to live up to its commitments. Argentina also entered bilateral investment treaties with the home countries of the members of AASA promising fair and equitable treatment of their investments in Argentina (the "fair-treatment provisions"). These treaties also established arbitration procedures to resolve disputes that might arise from investments in the signatory countries.

At the turn of this century, Argentina's economy fell into crisis, and its government responded with emergency regulatory measures. One measure unpegged Argentina's currency, the Argentine peso, from the U.S. dollar. Another froze the tariffs AASA could charge customers. Together these measures suppressed the peso's value and prevented AASA from increasing its prices, which led to a significant loss of revenue from its services. AASA had committed to repaying loans that were denominated in dollars and claimed that it could not pay for the quality of service that it had provided when the peso was more valuable unless something changed. Argentina denied AASA's repeated requests to alter the emergency measures or modify its obligations.

In 2003, the non-Argentine members of AASA began arbitration proceedings at the International Centre for Settlement of Investment Disputes (the "Centre") in Washington, D.C. The gravamen of their claim was that Argentina had breached its contract by treating them unfairly. Among its defenses, Argentina maintained that its conduct was compelled by the need to protect its economy and provide safe water. Three years into the arbitration, Argentina terminated the contract on the ground that AASA had failed to keep the nation's water supply free from contaminants. The arbitration lasted twelve years. At its conclusion in April 2015, a unanimous panel rejected Argentina's defense that its conduct was necessary to protect its economy and water supply and concluded that Argentina had breached the contract by treating AASA unfairly. The panel later awarded the claimants the profits they would have realized had Argentina honored the fair-treatment provisions.

In July 2015, Argentina brought suit in district court seeking to vacate the panel's award to AWG on two grounds. First, that the panel member selected by AASA was biased in favor of two of the non-Argentine consortium members. Although Argentina does not allege that the panel member had an outside interest in AWG, its fate in the arbitration was wrapped up with the fate of its fellow consortium members. Second, that the panel exceeded its authority by failing to credit Argentina's necessity defense and by compensating AASA with hypothetical profits earned after Argentina had lawfully terminated the contract. The district court rejected each of Argentina's arguments and granted AWG's cross-petition to enforce the award. Republic of Argentina v. AWG Grp. Ltd. , 211 F.Supp.3d 335 , 363 (D.D.C. 2016). Argentina timely appealed the district court's judgment.

II

The law of the United States governing arbitration is codified in the Federal Arbitration Act (the "Act"), 9 U.S.C. § 1 et seq. , which incorporates the United Nations Convention on the Recognition and Enforcement of Foreign Arbitral Awards, June 10, 1958, 21 U.S.T. 2517 (the "New York Convention"), in 9 U.S.C. §§ 201 - 08. The New York Convention is a multilateral treaty that requires signatory nations like the United States to honor the results of international arbitrations that comply with the treaty, but allows a court of the nation in which the arbitration was held to vacate the award if the proceeding violated that nation's domestic policy of fair adjudication. New York Convention art. V(2); 9 U.S.C. § 207 ; Enron Nigeria Power Holding, Ltd. v. Federal Republic of Nigeria , 844 F.3d 281 , 283 (D.C. Cir. 2016) ; TermoRio S.A. v. Electranta S.P. , 487 F.3d 928 , 935-36 (D.C. Cir. 2007). Under the New York Convention, the district court had authority to enforce or, if the arbitration violated the standards of fair adjudication set out in § 10 of the Act, vacate the award. 9 U.S.C. § 203 ; see also § 10(a). We have jurisdiction under 28 U.S.C. § 1291 to hear Argentina's appeal of the district court's decision, and we review the court's legal conclusions de novo. See Kurke v. Oscar Gruss & Son, Inc. , 454 F.3d 350 , 355 (D.C. Cir. 2006).

As a general matter, we will enforce an arbitration award unless given a compelling reason to suspect that the award resulted from an unfair process. See Hall St. Assocs. v. Mattel, Inc. , 552 U.S. 576 , 588, 128 S.Ct. 1396 , 170 L.Ed.2d 254 (2008) ("[L]imited review [is] needed to maintain arbitration's essential virtue of resolving disputes straightaway."); Dean Witter Reynolds, Inc. v. Byrd , 470 U.S. 213 , 221, 105 S.Ct. 1238 , 84 L.Ed.2d 158 (1985) ("[W]e rigorously enforce agreements to arbitrate ...."). Congress has pointedly endorsed private dispute resolution and directed courts to make the lawful judgments of arbitration panels effective. Epic Sys. Corp. v. Lewis , --- U.S. ----, 138 S.Ct. 1612 , 1621, --- L.Ed.2d ---- (2018) ("[Congress] specifically directed [courts] to respect and enforce ... parties' chosen arbitration procedures."); see also Preston v. Ferrer , 552 U.S. 346 , 353, 128 S.Ct. 978 , 169 L.Ed.2d 917 (2008) (describing the Act as establishing a national policy in favor of enforcing arbitration awards). Congress requires enforcement even when arbitration proceedings do not provide the full process protections that courts provide because the "primary purpose" of the Act is not to turn arbitration panels into private federal courts but to "ensure that private agreements to arbitrate are enforced according to their terms." Stolt-Nielsen S.A. v. AnimalFeeds Int'l Corp. , 559 U.S. 662 , 682, 130 S.Ct. 1758 , 176 L.Ed.2d 605 (2010) (internal quotation marks and citations omitted).

If we interfere with an arbitration decision, it is only because the proceeding deviated significantly from the Act's standards of fair adjudication. Oxford Health Plans LLC v. Sutter , 569 U.S. 564 , 568, 133 S.Ct. 2064 , 186 L.Ed.2d 113 (2013) ("Under the [Act], courts may vacate an arbitrator's decision 'only in very unusual circumstances.' " (quoting First Options of Chi., Inc. v. Kaplan , 514 U.S. 938 , 942, 115 S.Ct. 1920 , 131 L.Ed.2d 985 (1995) ) ); see also Hall St. Assocs. , 552 U.S. at 586, 128 S.Ct. 1396 ("Section[ ] 10 ... address[es] egregious departures from the parties' agreed-upon arbitration ...." (emphasis added) ). The burden to prove that there was unfair process falls on the challenger's shoulders, and it is "onerous." Al-Harbi v. Citibank, N.A. , 85 F.3d 680 , 683 (D.C. Cir. 1996) ; see also Encyclopaedia Universalis S.A. v. Encyclopaedia Britannica,Inc. , 403 F.3d 85 , 90 (2d Cir. 2005) (describing the burden on the challenger as a "heavy one"). If it were easy to call into question the fairness of an arbitration, losing parties would have every reason to challenge the process in court. Because arbitration's "essential virtue" is the avoidance of the length and expense of litigation, courts may grant relief to a disgruntled party only when its challenge to the arbitration is compelling. Hall St. Assocs. , 552 U.S. at 588, 128 S.Ct. 1396 ; see also Epic Sys. , 138 S.Ct. at 1621 ("[I]n Congress's judgment arbitration ... offer[s] ... the promise of quicker, more informal, and often cheaper resolutions for everyone involved.").

III

Impartiality of the arbitrators is a cardinal feature of fair adjudication. In 9 U.S.C. § 10 (a)(2), Congress permitted federal courts to set aside the results of arbitration "where there was evident partiality ... in the arbitrators." Argentina contends that there was evident partiality by one of the arbitrators because she sat on the board of directors for a company with investments in two of the parties.

At the outset of the arbitration proceedings, AASA chose as an arbitrator Professor Gabrielle Kaufmann-Kohler, a professor of arbitration at the University of Geneva; Argentina chose Professor Pedro Nikken, the former President of the Inter-American Court of Human Rights; and to chair the panel, the Centre chose and the parties approved Professor Jeswald W. Salacuse, an expert in international law. Three years into the proceedings, in April 2006, international financial-services company UBS AG ("UBS") appointed panel member Kaufmann-Kohler to serve on its board of directors. She was paid for her services in part with UBS stock and in part with a cash salary.

At the time of Kaufmann-Kohler's appointment, UBS managed trillions of dollars in investments, including over $2 billion in Suez and Vivendi. Most of those investments were made for the clients of UBS, who relied on the company to manage their funds. Only a sliver of the Suez and Vivendi shares were purchased as investments for UBS. Owning shares in Suez and Vivendi made UBS a passive shareholder without a management role or entitlement to the firms' profits.

When she accepted the position on the board of directors, Kaufmann-Kohler did not know of UBS's investments in Suez and Vivendi. UBS ran a check for any conflicts of interest she might have had with the company, and as part of that process Kaufmann-Kohler reported her activity as an arbitrator, including the arbitration involving Argentina, Suez, and Vivendi. The only conflict UBS identified was Kaufmann-Kohler's upcoming participation in the jury for the America's Cup race in which UBS had sponsored a yacht. UBS did not alert her to any connection the company had with Suez or Vivendi. In fact, Kaufmann-Kohler first learned of UBS's investments in them in November 2007, when Argentina sought her recusal from the panel because of her relationship with UBS. 1 The other members of the panel rejected Argentina's challenge, concluding that UBS's interests in Suez and Vivendi were too trivial to cause a reasonable person to doubt Kaufmann-Kohler's fairness. Even so, Kaufmann-Kohler resigned from the board on April 15, 2009, more than a year before the panel reached its decision finding Argentina liable to AASA.

We must decide whether Kaufmann-Kohler's brief service on the board obliged her to disclose to the arbitration parties her connections to Suez and Vivendi. The Act's "evident partiality" standard imposes duties on arbitrators with significant interests in the parties, a standard the Supreme Court examined in Commonwealth Coatings Corp. v. Continental Casualty Co. , 393 U.S. 145 , 89 S.Ct. 337 , 21 L.Ed.2d 301 (1968). There, the Court vacated an award because one of the three arbitrators did not disclose a prior substantial business relationship with a party to the arbitration proceeding. Id . at 150, 89 S.Ct. 337 . The arbitrator's "repeated and significant" consultations for that party on various business projects generated sizeable fees over time. Id . at 146, 89 S.Ct. 337 . Although there was no evidence that the arbitrator actually favored that party, the Court determined that his failure to disclose his interest in the party created a circumstance "[w]here there was evident partiality." Id . at 147-48, 89 S.Ct. 337 (quoting § 10(a)(2) ).

The Court agreed that disclosure was necessary, but the Justices could not agree on a single rationale. In his plurality opinion, Justice Black proposed adopting the same standard for avoiding partiality for arbitrators that governed judges. Id . at 148, 89 S.Ct. 337 . His rule would require arbitrators to disclose "any dealings that might create an impression of possible bias." Id . at 149, 89 S.Ct. 337 . In his mind, failing to disclose the exchange of a single dollar between an arbitrator and a party would violate the Act, even though that transaction likely would not have influenced the arbitrator. Id . at 147-48, 89 S.Ct. 337 .

In his concurrence, Justice White advanced a rule that relieves arbitrators from a duty to disclose trivial interests: "[A]rbitrators are not automatically disqualified by a business relationship with the parties before them if both parties are informed of the relationship in advance, or if they are unaware of the facts but the relationship is trivial." Id . at 150, 89 S.Ct. 337 . The exception for trivial interests relaxed the burden that a standard fit for federal judges would impose on professional arbitrators, whom Justice White distinguished as people "of affairs, not apart from but of the marketplace." Id . In Justice White's view, first-hand experience in the business world makes arbitrators especially adept at resolving the disagreements that arise in that world, and the Act did not create a disclosure duty so broad that it would drive away "the best informed and most capable potential arbitrators." Id . His interpretation of the Act would require an arbitrator to disclose an interest only when she "has a substantial interest in a firm which has done more than trivial business with a party." Id . at 150-52, 89 S.Ct. 337 . This is the rule we follow. 2

We applied Justice White's rule in Al-Harbi to uphold an award despite the arbitrator's undisclosed relationship with a party to the arbitration. 85 F.3d at 684 . There, unbeknownst to the arbitrator, his former law firm had previously represented the party on matters that were unrelated to the dispute submitted to the arbitration. Id . at 682-83. The challenger claimed the arbitration award should be vacated for evident partiality because the arbitrator had not investigated, and of course had not disclosed, the connection. Id . at 682.

Before considering whether evident partiality could apply when the arbitrator did not know he had an interest in the party, we first asked whether his interest was significant. See id . at 683. There is no duty to disclose a trivial interest under Commonwealth Coatings even if the arbitrator has full knowledge of his connection to the party. Id . We found that the challenger hadn't "establish[ed] specific facts that indicate[d] improper motives on the part of [the] arbitrator." Id . (quoting Peoples Sec. Life Ins. Co. v. Monumental Life Ins. Co. , 991 F.2d 141 , 146 (4th Cir. 1993) ). Because his interest was trivial, it could not give rise to evident partiality whether he knew about the interest or not. See id . ("[N]othing else appearing, the fact that an arbitrator has not conducted an investigation sufficient to uncover the existence of facts marginally disclosable under the Commonwealth Coatings duty is not sufficient to warrant vacating an arbitration award for evident partiality.").

We emphasized in Al-Harbi that a challenger to an arbitrator's partiality has a steep slope to climb. Id . (upholding the award in "light of [the] onerous standard for vacatur"). A challenger can satisfy its heavy burden of proof only by presenting "specific facts that indicate improper motives on the part of an arbitrator." Id . (quoting Peoples Sec. , 991 F.2d at 146 ). We conclude that the facts Argentina sets forth fail to meet that high standard.

Argentina contends that a reasonable person would think the huge sum of money UBS invested in Suez and Vivendi biased Kaufmann-Kohler in their favor because of her position on the UBS board. This appearance of bias would, in Argentina's view, trigger a duty for Kaufmann-Kohler to disclose the investments UBS made in the parties before she joined its board of directors. AWG responds that Kaufmann-Kohler did not need to discover and disclose the investments because her connection with Suez and Vivendi was remote-so remote, in fact, that she hadn't even known about the investments.