I think, since federal crimes are [promulgated and made possible solely by stating that an offense has a nexus with interstate commerce, that the feds should have to, as an element of the offense, prove that interstate commerce was implicated.
For instance, a former prosecutor (and not my favorite folks, btw) in Montana faces 20 years of prison time for buying cocaine and letting his guests snort it at parties. Is it criminal under state law? Sure. Is it 20 years-worthy, with no parole, under the federal system? You bet your sweet ass it's not. And why? Because it's a federal crime, implicating "interstate commerce".
If that's really the case, on the consumer's end, then make these damned cripple-beating feds prove that this guy engaged in economic activity across state lines, or that cocaine here was an instrumentality of interstate commerce, or that his few lines had a cumulative effect on interstate commerce. Until then, it's a bullshit war on "drugs" that is, in actuality, a war on people.