Legal Question in Constitutional Law in Colorado

Yes. Possession of marijuana is a federal crime. Federal laws apply throughout the U.S. It used to be that all 50 states *also* criminalized possession of marijuana. Some no longer do, at least in some circumstances. But all this means is that it's now possible to violate only one set of criminal laws by possessing pot instead of two. It does not mean you can do so legally anywhere in the U.S.

The federal government doesn't often prosecute people for simple possession of marijuana. But sometimes it does, and it can still decide to do so more often if it wants to.