term “ex post facto ” literally describes any law passed “after the fact,” it is well established that this provision applies only to criminal punishments. See Collins v. Youngblood, 497 U.S. 37, 41, 110 S.Ct. 2715, 111 L.Ed.2d 30 (1990). A law violates the ex post facto prohibition if it applies to events occurring before its enactment and causes an offender affected by it to suffer a disadvantage, either by altering the definition of particular criminal conduct or by increasing the punishment for the crime. See id. at 50, 110 S.Ct. 2715; see also Weaver v. Graham, 450 U.S. 24, 29, 101 S.Ct. 960, 67 L.Ed.2d 17 (1981).
The North Dakota Supreme Court rejected Mr. Burr’s argument because it concluded that the registration statute was not punitive, even though it had a retrospective effect. See Burr, 598 N.W.2d at 159. We hold that this decision is neither “contrary to,” nor “an unreasonable application of, clearly established Federal law, as determined by the Supreme Court of the United States,” see 28 U.S.C. § 2254(d)(1); see also Williams v. Taylor, 529 U.S. 362, --, 120 S.Ct. 1495, 1519-23, 146 L.Ed.2d 389 (2000).
In reaching its decision, the North Dakota Supreme Court began with an examination of the legislative history of the registration statute. See Burr, 598 N.W.2d at 152-53. It found no evidence that the legislature sought to increase the penalty for sex crimes or intended to use registration as a punishment. See id. at 153. The North Dakota Supreme Court then proceeded to determine whether the registration statute was punitive in its actual effect. See id. at 153-59. For this analysis, see id., it relied on the holding of the Supreme Court of the United States in Kennedy v. Mendoza-Martinez, 372 U.S. 144, 169, 83 S.Ct. 554, 9 L.Ed.2d 644 (1963).
Mendoza-MaHinez identifies seven considerations that serve as guideposts for deciding whether a law is punitive. These considerations are: (1) whether the sanction involves an affirmative disability or restraint; (2) whether it has historically been regarded as punishment; (3) whether it comes into play only on a finding of scienter; (4) whether its operation will promote the traditional aims of punishment, which are retribution and deterrence; (5) whether the behavior to which it applies is already a crime; (6) whether an alternative purpose to which it may rationally be connected is assignable to it; and (7) whether it appears excessive in relation to the alternative purpose assigned. See id. at 168-69. The North Dakota Supreme Court considered these matters in relation to the registration statute and held that the law was not punitive. See Burr, 598 N.W.2d at 158-59. It observed that a requirement to register did not impose on Mr. Burr any affirmative disability or restraint. See id. at 154. It also noted that this requirement did not fit within any traditional notion of what was punishment. See id. Finally, the North Dakota Supreme Court ruled that the registration statute furthered a “legitimate,” see id. at 159, public interest of protecting communities from sexual predators and was not excessive in the context of its “important,” see id. at 156, purpose.
We believe that the North Dakota Supreme Court applied the appropriate legal standard in this case, and we cannot say that its decision was unreasonable in light of any clearly established legal principle as determined by the Supreme Court of the United States. We note, as Mr. Burr concedes in his brief, that “there is no single bright-line test for what constitutes punishment,” and that an application of Mendoza-MaHinez usually involves a certain degree of judicial discretion: Some of the considerations identified in that case may be more or less dispositive than others. See Hudson v. United States, 522 U.S. 93, 101, 118 S.Ct. 488, 139 L.Ed.2d 450 (1997). Courts are free, moreover, to weigh additional considerations beyond those identified in Mendoza-Martinez. See United States v. Ward, 448 U.S. 242, 249, 100