There's a quote right in the Wikipedia article which talks about the practical reasoning and historical basis for the decision: > Even respondents acknowledge

There's a quote right in the Wikipedia article which talks about the practical reasoning and historical basis for the decision: > 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.