Article I, Section 9, Clause 3:

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

An ex post facto law, named using the Latin phrase for “after the fact,” is a law that imposes criminal liability or increases criminal punishment retroactively.1 Two separate clauses of the Constitution, Article I, Sections 9 and 10, respectively ban enactment of ex post facto laws by the Federal Government and the states.2

In the Federalist No. 44, James Madison asserted that ex post facto laws “are contrary to the first principles of the social compact, and to every principle of sound legislation.” 3 In the Federalist No. 84, Alexander Hamilton further justified prohibitions on ex post facto laws by arguing:

The prohibition on ex post facto laws seeks “to assure that legislative Acts give fair warning of their effect and permit individuals to rely on their meaning until explicitly changed” and “restricts governmental power by restraining arbitrary and potentially vindictive legislation.” 5 The Supreme Court has further stated that the prohibition is based on

At the Constitutional Convention, multiple delegates expressed disapproval of ex post facto laws. However, some believed that an explicit constitutional prohibition of ex post facto laws was unnecessary because such laws were clearly invalid. One delegate “contended that there was no lawyer, no civilian who would not say that ex post facto laws were void of themselves.” 7 Others asserted that including the prohibition could do harm by “proclaim[ing] that we are ignorant of the first principles of Legislation, or are constituting a Government which will be so” or “implying an improper suspicion of the National Legislature.” 8 Other delegates responded that an express prohibition was necessary because some state legislatures had previously passed ex post facto laws, and state constitutional bans of such laws had been invoked to oppose them.9

There was also discussion at the Convention as to whether the prohibition on ex post facto laws applied only to retroactive criminal laws or also forbade retroactive civil laws.10 The delegates rejected a suggestion that would have altered the federal Ex Post Facto Clause to state expressly that it applied to civil laws, but they did not clearly resolve the question.11 Soon after ratification, in the 1798 case Calder v. Bull, the Supreme Court construed the constitutional prohibition on ex post facto laws to prohibit only retroactive criminal laws.12

Footnotes

1

E.g., Locke v. New Orleans, 71 U.S. 172, 173 (1867).

2

For the prohibition on state ex post facto laws, see U.S. Const. art. I, § 10, cl. 1. See also ArtI.S10.C1.5 State Ex Post Facto Laws.

3

The Federalist No. 44, at 278–79 (James Madison). Madison further noted that several state constitutions expressly banned ex post facto laws and that in any case such laws were “prohibited by the spirit and scope of these fundamental charters.” Id.

4

The Federalist No. 84, at 511 (Alexander Hamilton).

5

Weaver v. Graham, 450 U.S. 24, 28–29 (1981).

6

Beazell v. Ohio, 269 U.S. 167, 170 (1925). By contrast, the Supreme Court has held that retroactive criminal statutes that do not disadvantage criminal defendants are not ex post facto laws. See ArtI.S9.C3.3.5 Increasing Punishment and Ex Post Facto Laws.

7

2 The Records of the Federal Convention of 1787, at 376 (Max Farrand ed., 1911).

8

Id.

9

Id.

10

Id. at 448–49, 617.

11

Id. at 617. See also id. at 440 (considering amendment to the state Ex Post Facto Clause that would instead have prohibited enactment of “retrospective laws” ).

12

3 U.S. 386, 389 (1798). See also 3 Joseph Story, Commentaries on the Constitution of the United States § 1339 (1833).