Petitioner Gregory Wilson, who is an inmate at a Department of Corrections institution, and his wife Stormii Wilson, who is not, challenge the validity of a department rule that prohibits inmates from receiving “[s]exually explicit material which by its nature or content poses a threat or is detrimental to the security, good order or discipline of the facility, inmate rehabilitation, or facilitates criminal activity ***” OAR 291-131-0035(l)(a).1 Petitioners contend that the rule violates their freedom of expression as guaranteed *556by Article I, section 8, of the Oregon Constitution. We conclude that the rule, on its face, is not unconstitutional. We therefore reject petitioners’ challenge.

Petitioners advance a facial challenge under ORS 183.400(1)2 — that is, they contend that the department created a rule that is unlawful per se, apart from any particular application or set of circumstances. See State v. Johnson, 238 Or App 672, 675-76, 243 P3d 805 (2010) (describing facial challenge). In reviewing such challenges, we are limited to consideration of the rule itself, statutory provisions authorizing the rule, and documents bearing on compliance with rulemaking procedures. ORS 183.400(3); AFSCME Local 2623 v. Dept. of Corrections, 315 Or 74, 79, 843 P2d 409 (1992). We may declare a rule invalid only if, based on those sources, we conclude that the rule violates a constitutional provision, exceeds the agency’s statutory authority, or was adopted without compliance with applicable rulemaking procedures. ORS 183.400(4); Estes v. Dept. of Corrections, 210 Or App 399, 401, 150 P3d 1088, rev den, 342 Or 523 (2007).

Petitioners do not allege that the adoption of the rule was procedurally invalid. They do, however, assert that the rule exceeds the department’s statutory authority and that it is unconstitutional. Their argument regarding the department’s authority rests on two premises. The first is that the department has no authority to regulate the conduct of persons such as Stormii Wilson, who is not incarcerated. That premise is unsupportable. The rule regulates the receipt, by inmates, of material sent by noninmates, and regulates noninmates’ conduct only when that conduct reaches into the institution and threatens its operations. Petitioners’ second premise underlying the theory that the rule exceeds the department’s statutory authority is that the department *557has no authority to promulgate unconstitutional rules. That ultra vires argument collapses into the constitutional argument; thus, the only question before us is whether the rule violates Article I, section 8.3

To answer that question, we must first construe the rule. In doing so, we note one important feature. In order to justify the confiscation of mail or its return to sender, department authorities must make a number of individualized judgments. First, they must determine that the particular material at issue is sexually explicit. Petitioners do not allege, and we do not conclude, that that language, including the exceptions and a noninclusive list of examples, is unconstitutionally vague. Next, and significantly, the department must determine that the particular sexually explicit material “by its nature or content poses a threat or is detrimental to the security, good order or discipline of the facility, inmate rehabilitation, or facilitates criminal activity.” OAR 291-131-0035(l)(a). The rule, then, does not apply to all material that is characterized as “sexually explicit,” but only “sexually explicit material which by its nature or content” threatens specified harms. Id. (emphasis added). The necessary implication of that language is that some sexually explicit material does not pose a threat of harm and is therefore permitted, and the necessary implication of that implication is that some department official makes a case-by-case determination as to each piece of sexually explicit material.4 Such determinations, of course, may be vulnerable to an as-applied challenge.

*558With that understanding, we readily conclude that OAR 291-131-0035(1) does not, on its face, violate Article I, section 8.

“Oregon free speech jurisprudence divides laws that might implicate expression into three categories: laws that explicitly and in terms prohibit speech itself, regardless of whether the speech causes or is an attempt to cause harm; laws that prohibit the accomplishment of, or attempt to accomplish, harm and specify that one way that the harm might be caused is by speech; and laws that, without reference to or specification of speech, prohibit the accomplishment of, or attempt to accomplish, harm that, in some circumstances, could be caused by speech. State v. Plowman, 314 Or 157, 163-64, 838 P2d 558 (1992), cert den, 508 US 974 (1993). An example of the first kind of law is a statute prohibiting obscenity. See State v. Henry, 302 Or 510, 732 P2d 9 (1987). Such laws are facially unconstitutional ‘unless the scope of the restraint is wholly confined within some historical exception that was well established when the first American guarantees of freedom of expression were adopted and that the guarantees then or in 1859 demonstrably were not intended to reach.’ State v. Robertson, 293 Or 402, 412, 649 P2d 569 (1982). An example of the second kind of law is a statute prohibiting one person from using a verbal threat to coerce another person into doing something she does not want to do. Id. at 415. Such laws are presumptively constitutional unless they are incurably overbroad. Id. at 417-18. An example of the third type of law is a trespass statute that, although it does not mention expressive activity, could be enforced against political protesters engaging in political expression. See City of Eugene v. Lincoln, 183 Or App 36, 50 P3d 1253 (2002). Such laws are facially constitutional; whether applying them violates Article I, section 8, depends necessarily on the facts of a particular case. Robertson, 293 Or at 417.”

State v. Rich, 218 Or App 642, 646, 180 P3d 744 (2008).

*559OAR 291-131-0035(1) falls into the second category of rules that might implicate expression. The rule specifies a variety of harms and prohibits expression only when it would pose a threat of one or another of those harms; as explained above, sexually explicit expression that does not pose such a threat of harm is not prohibited. Thus, the dis-positive question is whether, in limiting expression in order to prevent harm, the rule is incurably overbroad, that is, whether the rule would prevent a harm that obviously lies beyond the authority of the lawmaker to prevent. A classic example is a law prohibiting expression that alarms a person, which would prohibit a physician from telling a patient that her smoking habit is shortening her life expectancy, or a political candidate from telling an audience that, if her opponent is elected, property taxes will double.

Petitioners suggest no situations, and we can contemplate none, in which the application of OAR 291-131-0035(1) would result in the prohibition of obviously unreg-ulable expression. Put another way, we can think of no prohibited speech that does threaten prison security, impede inmate rehabilitation, or facilitate crime, yet is nonetheless protected. If such situations exist, they do not amount to significant overbreadth. Thus, OAR 291-131-0035(1) does not, on its face, violate Article I, section 8.

OAR 291-131-0035 held valid.