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529US2

Unit: $U52

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Cite as: 529 U. S. 513 (2000)

521

Opinion of the Court

tioner’s pro se petition for certiorari, 527 U. S. 1002 (1999),
and appointed counsel, id., at 1051.

II

To prohibit legislative Acts “contrary to the ﬁrst princi-
ples of the social compact and to every principle of sound
legislation,” 6 the Framers included provisions they con-
sidered to be “perhaps greater securities to liberty and re-
publicanism than any [the Constitution] contains.” 7 The
provisions declare:

“No State shall . . . pass any Bill of Attainder, ex post
facto Law, or Law impairing the Obligation of Con-
tracts . . . .” U. S. Const., Art. I, § 10.8

The proscription against ex post facto laws “necessarily
requires some explanation; for, naked and without expla-
nation, it is unintelligible, and means nothing.” Calder v.
Bull, 3 Dall. 386, 390 (1798) (Chase, J.).
In Calder v. Bull,
Justice Chase stated that the necessary explanation is de-
rived from English common law well known to the Fram-
ers: “The expressions ‘ex post facto laws,’ are technical, they
had been in use long before the Revolution, and had acquired
an appropriate meaning, by Legislators, Lawyers, and Au-
Id., at 391; see also id., at 389 (“The prohibition . . .
thors.”
very probably arose from the knowledge, that the Parlia-
ment of Great Britain claimed and exercised a power to pass
such laws . . .”); id., at 396 (Paterson, J.). Speciﬁcally, the

facto violation); Murphy v. Sowders, 801 F. 2d 205 (CA6 1986) (same);
Murphy v. Kentucky, 652 S. W. 2d 69 (Ky. 1983) (same). See also Idaho
v. Byers, 102 Idaho 159, 627 P. 2d 788 (1981) ( judicial change in witness
corroboration rule may not be applied retroactively); Bowyer v. United
States, 422 A. 2d 973 (DC 1980) (same).

6 The Federalist No. 44, p. 282 (C. Rossiter ed. 1961) (J. Madison).
7 Id., No. 84, at 511 (A. Hamilton).
8 Article I, § 9, cl. 3, has a similar prohibition applicable to Congress:

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