From the SCOTUS ruling:
Banning the growing of marijuana for medical use, the Court reasoned, was a permissible way of preventing or limiting access to marijuana for other uses:
"Even respondents acknowledge the existence of an illicit market in marijuana; indeed, Raich has personally participated in that market, and Monson expresses a willingness to do so in the future. More concretely, one concern prompting inclusion of wheat grown for home consumption in the 1938 Act was that rising market prices could draw such wheat into the interstate market, resulting in lower market prices. Wickard, 317 U.S., at 128. The parallel concern making it appropriate to include marijuana grown for home consumption in the CSA is the likelihood that the high demand in the interstate market will draw such marijuana into that market. While the diversion of homegrown wheat tended to frustrate the federal interest in stabilizing prices by regulating the volume of commercial transactions in the interstate market, the diversion of homegrown marijuana tends to frustrate the federal interest in eliminating commercial transactions in the interstate market in their entirety. In both cases, the regulation is squarely within Congress' commerce power because production of the commodity meant for home consumption, be it wheat or marijuana, has a substantial effect on supply and demand in the national market for that commodity"
http://en.wikipedia.org/wiki/Gonzales_v._Raich
Now THAT is freaking classic! The Court is saying two things. The first is that Congress can ban or tax your vegetable garden because it means you aren't buying food at the store. Therefore, you are engaed in interstate commerse by not engaing in it.

But, wait, there's more, and its better than a bamboo steamer!
.They go on to say that Congress can regulate interstate commerce that it has banned., So basically, even though selling pot is illegal, by growing your own you are effecting interstate commerce by not patronizing your local dealer, which, by the way is a felony. WTF?

Tell me the justices weren't smoking something a lot more potent than pot.