I agree it is a Federal Offense and is a point of contention with States, that said....
It will come down to how much enforcement the Fed decides to put on it. They can turn their head and they are in a lot of cases.
Fed law does trump State law even if States don't want to admit it. Go back in time and you'll see where the Fed decided to impose their will on Racial Matters of the 60's in states where they decided that segregation was still OK...
They may come down hard but they also may not. Sure they are hardballing a few but that is a small fraction of what is going on... All those Med marijuana dispensaries are getting it from somewhere.
Funny how it is illegal for me to smoke pot because it is so harmful that the government feels the need to protect me but it is OK for me to smoke poison ivy.