Article I, Section 9, Clause 3:

No Bill of Attainder or ex post facto Law shall be passed.

Separate provisions of the Constitution ban enactment of ex post facto laws by the Federal Government and the states, respectively.1 The Supreme Court has cited cases interpreting the federal Ex Post Facto Clause in challenges under the state clause, and vice versa, implying that the two clauses have the same scope.2 The Court has construed both clauses to ban legislatures from enacting laws that impose criminal liability or increase criminal punishment retroactively.3 The constitutional prohibitions of ex post facto laws are closely related to the prohibitions of bills of attainder—legislative actions that determine guilt or impose criminal punishment on specific persons or groups without a judicial trial.4 In some cases, the Court has held that a single legislative action may violate both the ex post facto and bill of attainder prohibitions.5

Some ex post facto cases involve facial challenges—claims that the challenged laws are invalid in all circumstances.6 Many, however, involve claims that the Ex Post Facto Clauses bar applying laws to specific offenses that were committed before the laws’ enactment.7 The Supreme Court has denied ex post facto claims when it has found that a law is not ex post facto as applied to the challenger, even when the law might be ex post facto as applied to others not before the Court.8

The Supreme Court has held that the constitutional prohibitions on ex post facto laws do not apply to crimes committed outside the jurisdiction of the United States against the laws of a foreign country.9

Footnotes

1

U.S. Const. art. I, § 9, cl. 3; art. I, § 10, cl. 1. While there are two Ex Post Facto Clauses, only one of the two can apply to any given piece of legislation. Courts and commentators at times distinguish between the federal Ex Post Facto Clause and the state Ex Post Facto Clause, but also sometimes use the singular “Ex Post Facto Clause” without explicitly distinguishing between the two. E.g., Dorsey v. United. States 567 U.S. 260, 275 (2012) ( “Although the Constitution’s Ex Post Facto Clause, Art. I, § 9, cl. 3, prohibits applying a new Act’s higher penalties to pre-Act conduct, it does not prohibit applying lower penalties.” ).

2

See, e.g., Peugh v. United States, 569 U.S. 530, 532–33 (2013) (case construing federal clause citing case construing state clause); Reetz v. Michigan, 188 U.S. 505, 510 (1903) (case construing state clause citing case construing federal clause).

3

See, e.g., Calder, 3 U.S. at 389; Peugh, 569 U.S. at 532–33; Baltimore and Susquehanna R.R. v. Nesbit, 51 U.S. 395, 401 (1850) (a state can enact a retroactive law that is not punitive and does not impair the obligation of contracts). See also Fletcher v. Peck, 10 U.S. 87, 138 (1810) ( “An ex post facto law is one which renders an act punishable in a manner in which it was not punishable when it was committed.” ); Locke v. New Orleans, 71 U.S. 172, 173 (1867); Orr v. Gilman, 183 U.S. 278, 285 (1902).

4

E.g., Nixon v. Adm’r of Gen. Servs., 433 U.S. 425, 537–38 (1977).

5

E.g., Cummings v. Missouri, 71 U.S. 277 (1866); Ex parte Garland, 71 U.S. 333 (1866).

6

See, e.g., Garland, 71 U.S. at 382; cf. Jaehne v. New York, 128 U.S. 189, 194 (1888) (challenger argued that a law was facially invalid because it could be ex post facto in some cases).

7

See, e.g., Lindsey v. Washington, 301 U.S. 397, 398 (1937); Weaver v. Graham, 450 U.S. 24, 28–33 (1981).

8

Jaehne, 128 U.S. at 194 (law that might be void as applied to pre-enactment offenses was not void as applied to post-enactment offenses); Bugajewitz v. Adams, 228 U.S. 585, 608–09 (1913).

9

Neely v. Henkel, 180 U.S. 109, 123 (1901).