The Supreme Court, in Peugh v. United States, ruled that the ex post facto clause requires federal criminal defendants to be sentenced under the Guidelines in effect when the crime occurred, not higher guidelines in place at the time of sentencing. There are a number of guidelines that have become more harsh over time, including those for many fraud offenses.

Peugh was convicted of bank fraud and sentenced to 70 months of imprisonment under sentencing guidelines that had been increased in 2009. But his crimes had occurred in 1999 and 2000, and he should have been sentenced under the 1999 guidelines, which would have dictated a sentencing range of 30-37 months.

Justice Sotomayor wrote the majority opinion, rejecting an argument that the sentencing guidelines are only advisory after the Booker decision, and therefore do not have the effect of increasing sentences after the fact. Instead, she explained that because the district courts are required to use the sentencing guidelines as a starting point in their sentencing analysis, they still create a sufficient risk of an increased sentence that they trigger the ex post facto clause of the Constitution.

Whether this decision will lead to dramatic reductions in sentences for fraud defendants remains to be seen. At resentencing hearings for defendants who challenge their sentences following Peugh, district courts will have to recalculate the applicable guideline range. But, those courts will not be bound by the range, and may elect to justify their original sentences under the statutory factors in 18 U.S.C. §3553.