It's complicated and far from a settled issue. As far as I understand it you can be arrested by federal law enforcement and charged with a federal crime but yo

It's complicated and far from a settled issue. As far as I understand it you can be arrested by federal law enforcement and charged with a federal crime but you cannot be arrested by local or state law enforcement and charged with a local or state crime. This is why the marijuana industry is "cash only" - banks won't give them a bank account because it violates federal law for them to do so. This is very undesirable for the marijuana companies because having large stacks of cash laying around is a liability and also an accounting mess. Though last I heard some companies might be trying to band together to create a "maybe semi legal bank like entity" to fix this problem. So far the DEA has largely chosen not to go after marijuana dispensaries and growers that are operating within the parameters of state law, but that can change, and it might lead to some interesting court cases. This also can lead to problems for ordinary citizens, if they can go into a store and buy a product it is reasonable to think the product is totally and completely legal. However, they do risk being charged with a federal crime, but that's not totally obvious.