The various defendants here were sentenced for conspiracy charges based on methamphetamine. In each case, the sentencing judge found that the mandatory minimum sentence the defendant was facing exceeded the maximum for the Guideline range the defendant was facing. In each case, the Government filed motions indicating that the defendants offered substantial assistance to the Government, leading to a reduction in sentence from that mandatory minimum.
Years later, the Sentencing Commission lowered the Guidelines range for this offense. In a case where a defendant is sentenced under a Guidelines range that is subsequently lowered, such a defendant can move for a sentencing reduction under 18 U. S. C. §3582(c)(2). These defendants argued that they were eligible for such relief.
The U.S. Supreme Court disagreed, unanimously holding that these defendants were sentenced based on a mandatory minimum, not the sentencing guideline range. They therefore found that the defendants were therefore ineligible for
§3582(c)(2) sentence reductions.
The case is Koons v. United States, 17-1516.
https://www.supremecourt.gov/opinions/17pdf/17-5716_jhek.pdf