Ex Post Facto Clause

Ex post facto laws are laws which apply to an event which occurred in the past. They are a form of retroactive legislation. Most are enacted as an attempt by a legislature to identify specifically one person or group of persons who are to be punished by the legislation. The U.S. Constitution prohibits such retroactive legislation in Article I, section 9, clause 3. While this is a constitutional provision that only applies to the federal government, a parallel provision in Article I, section 10, clause 1, applies to the states.

The twin constitutional provisions prohibiting ex post facto laws were limited in their application by the U.S. Supreme Court in the 1798 decision of Calder v. Bull (1798). The Court held that legislatures can not pass a law subjecting someone to a fine or period of imprisonment for an act that was not unlawful when it was done. This meant that the ex post facto provisions in the U.S. Constitution would apply only to penal and criminal statutes. In addition to limiting the application of the ex post facto provisions, Justice Samuel Chase suggested strongly that many types of retroactive legislation are generally unjust and as a general rule should be avoided.

In his opinion, Justice Chase wrote the authoritative formulation of the kinds of retroactive legislation that would fall within the Constitution’s prohibition of ex post facto legislation:

1st. Every law that makes an action done before the passing of the law, and which was innocent when done, criminal; and punishes such action. 2d. Every law that aggravates a crime, or makes it greater than it was, when committed. 3d. Every law that changes the punishment, and inflicts a greater punishment, than the law annexed to the crime, when committed. 4th Every law that alters the legal rules of evidence, and receives less, or different testimony, than the law required at the time of the commission of the offence, in order to convict the offender.

The Supreme Court’s decision in Calder v. Bull reflected the ideas of many of this nation’s founders. Alexander Hamilton had written, for example, in The Federalist Papers Number 84 of a strong opposition to ‘‘ [t]he creation of crimes after the commission of the fact, or, in other words, the subjecting of men to punishment for things which, when they were done, were breaches of no law . . .’’

The essential character of all ex post facto legislation is its retroactive application. But within the meaning of the prohibition as defined in Calder v. Bull, not all retroactive legislation is barred by the Constitution’s dual provisions. For example, laws that require the deportation of certain aliens for past conduct have been held as not penalizing a person for his or her past conduct. One such case is Marcello v. Bonds (1955) where an order deporting a resident alien was affirmed by the Supreme Court because of an earlier drug conviction. Other laws, such as those challenged in Kansas v. Hendricks (1997), which have changed the length or nature of the incarceration for certain convicted sexual offenders have been held to be civil in nature. Thus, the additional commitment to a mental health facility because the offender was determined to be a danger to self or to others has been upheld.

A provision enacted by the California legislature, which extended the statute of limitations for a crime beyond the one-year period for prosecution following the commitment of the crime, was found in Stogner v. California (2003) to violate the ex post facto barrier when the purpose was to revive a previously timebarred prosecution. The allegations in the Stogner prosecution were that the alleged sexual offenses had occurred more than twenty years prior to the revision of California’s three-year statute of limitations. This distinction between civil and penal laws was also made in the decision in Smith v. Doe (2003) in the same U.S. Supreme Court term upholding the application of provisions of Alaska’s ‘‘Megan’s Law,’’ which required convicted sex offenders to register with local police departments. The Supreme Court noted that the legislature intended to create a civil regulatory scheme and one that was not clearly punitive in nature.

Three considerations usually underlie any evaluation of enacted ex post facto laws. First, ex post facto laws are generally believed to violate the Constitution’s separation of powers. The Constitution assigns to the executive and judicial branches the responsibility for handing out punishment against individuals found to have committed crimes. The legislative branch, by contrast, is expected to make laws of general application. Second, ex post facto laws may violate First Amendment principles if the intended punishment is seen to have a chilling effect on otherwise constitutionally protected speech or actions. And, third, ex post facto laws are generally unfair in that they fail to provide adequate notice to individuals that their actions may have criminal consequences.


References and Further Reading

  • Congressional Research Service. The Constitution of the United States of America: Analysis and Interpretation. Washington, D.C.: U.S. Government Printing Office, 2004.
  • Monk, Linda R. The Words We Live By: Your Annotated Guide to the Constitution. New York: Hyperion, 2003.
  • Rotunda, Ronald D., and John E. Nowak. Treatise on Constitutional Law: Substance and Procedure. 3rd ed. St. Paul, MN: West Group, 1999.

Cases and Statutes Cited

  • Calder v. Bull, 3 U.S. (3 Dall.) 386 (1798)
  • Kansas v. Hendricks, 521 U.S. 346 (1997)
  • Marcello v. Bonds, 349 U.S. 302 (1955)
  • Smith v. Doe, 538 U.S. 84 (2003)
  • Stogner v. California, 539 U.S. 607 (2003)


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