for things which, when they were done, were breaches of no law" has been "in all ages" one of "the favorite and most formidable instruments of tyranny." Indeed, ex post facto legislation has generally been regarded as a violation of the fundamental DUE PROCESS requirement that there must be fair warning of the conduct which gives rise to criminal penalties. The Framers of the Constitution believed so strongly that ex post facto laws were contrary to the principles of republican government that they proscribed their use in two different provisions of the Constitution: Article I, section 9, as a specific exception to the powers of the United States Congress, and Article I, section 10, as a specific prohibition on the powers of state legislatures.
Justice SAMUEL CHASE in CALDER V. BULL (1798) provided what has since come to be regarded as the authoritative delineation of the kinds of LEGISLATION that fall within the Constitution's prohibition against ex post facto enactments:
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 received less, or different, testimony, than the law required at the time of the commission of the offence, in order to convict the offender.
Although there is some question about the Framers' intent, the Supreme Court has consistently followed Chase's lead in restricting the ex post facto rule to criminal laws. Thus the Court has held that the deportation of ALIENS, the loss of a passport, and the denial of certain benefits do not fall within the ex post facto exception because they are not punishments in a criminal sense even though they may be "burdensome and severe." In the TEST OATH CASES (1867), however, the Court held that oaths that disqualified people from holding certain offices or practicing certain professions constituted ex post facto laws.
The essential ingredient of an ex post facto law is its retrospective character; but not all...