You might want to read the 10th amendment:

The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.

You can affirm that we are not delegating the enforcement of cannabis related laws by reading the text of Alaska Statute 11.71.190 which classifies cannabis as a schedule VIa controlled substance.

The definition of a schedule VIa controlled substance is:

A substance shall be placed in schedule VIA if it is found under AS 11.71.120 (c) to have the lowest degree of danger or probable danger to a person or the public.

This is relative to the federal classification as a schedule I.