We granted certiorari, 479 U. S. 960 (1986), and now reverse.
II
Article I of the United States Constitution provides that neither Congress nor any State shall pass any “ex post facto Law.” See Art. I, §9, cl. 3; Art. I, §10, cl. 1. Our understanding of what is meant by ex post facto largely derives from the case of Calder v. Bull, 3 Dall. 386 (1798), in which this Court first considered the scope of the ex post facto prohibition. In Calder, Justice Chase, noting that the expression “ex post facto” “had been in use long before the revolution,” id., at 391, summarized his understanding of what fell “within the words and the intent of the prohibition”:
“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 offense, in order to convict the offender.” Id., at 390 (emphasis omitted).
Accord, Dobbert v. Florida, supra, at 292, quoting Beazell v. Ohio, 269 U. S. 167, 169-170 (1925).
Justice Chase explained that the reason the Ex Post Facto Clauses were included in the Constitution was to assure that federal and state legislatures were restrained from enacting arbitrary or vindictive legislation. See 3 Dall., at 389. Justices Paterson and Iredell, in their separate opinions in Calder, likewise emphasized that the Clauses were aimed at preventing legislative abuses. See id., at 396 (Paterson, J.); id., at 399-400 (Iredell, J.). See also Malloy v. South Carolina, 237 U. S. 180, 183 (1915); James v. United States, 366