The following excerpt is from U.S. v. Restrepo, 903 F.2d 648 (9th Cir. 1990):
A criminal law is ex post facto if it satisfies two requirements: it must apply retrospectively to events occurring before its enactment, and it must disadvantage the defendant affected by it. Miller v. Florida, 482 U.S. 423, 430, 107 S.Ct. 2446, 2451, 96 L.Ed.2d 351 (1987). Additionally, "no ex post facto violation occurs if a change does not alter 'substantial personal rights,' but merely changes 'modes of procedure which do not affect matters of substance.' " Id. (citation omitted).
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