Whether, under the categorical approach established by this Court for
determining whether a previous state conviction can qualify as a predicate "serious
drug offense" under the Armed Career Criminal Act (ACCA), a sentencing court is to
apply the federal definition of "controlled substance" as it existed (1) at the time of
the prior state conviction, (2) at the time of the commission of the federal offense, or
(3) at the time of federal sentencing.

Whether the categorical approach for determining a 'serious drug offense' under the Armed Career Criminal Act applies the federal definition of 'controlled substance' at the time of the prior state conviction, the federal offense, or federal sentencing