Feeney Amendment and ex post facto laws

Ruling it is "procedural rather than substantive," the 2nd U.S. Circuit Court of Appeals has joined other circuits in applying the PROTECT Act's de novo review of federal sentences to appeals that were pending when the act was passed.
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Pre-Feeney, a judge's decision to grant a downward departure was subject to an abuse of discretion standard of review. (Koon v. United States). The Feeney Amendment provided that sentencing decisions would not be subject to de novo review. The Feeney Amendment applied retroactively.

The legal issue is fascinating. We know that a change in a rule of evidence that makes it easier for the prosecution to prove a defendant's guilt violates the ex post facto clause. It seems to me that a procedural rule that makes a harsher sentence more likely also violates the ex post facto clause.