I wonder if USCG enforcement will be predicated by state registration vs. US documention? Down here in the Caribbean, there are no recreational or medical pot legislations. It's all illegal and yet very common. And, as someone pointed out earlier; under the Reagan directive, gave the USCG the right to board your US flag vessel anywhere in the world for any reason! Boardings are common in the island chain and are the subject of a lot of discussion among cruisers. They, (the USCG) board boats from many nations for "routine law enforcement inspection." They bypass normal protocols by having a member or two from the local jurisdictions on board. Thus, the boardings become legal.
Controlling your own vessel is your best defense. I remember years ago when a little old lady, of some 72 years, was asked by the judge how she smoked for all those years without detection.... She replied, "if you don't smoke pot, you don't know anyone who does. But when you do smoke pot, you don't know anyone who doesn't!" Sometimes you just don't know.