After Lopez and Morrison, some wondered what level of review would apply in Commerce Clause decisions. It seems that rational basis rules.
Per Justice Stevens, writing for a 6-3 Court: In Wickard, we had no difficulty concluding that Congress had a rational basis for believing that, when viewed in the aggregate, leaving home-consumed wheat outside the regulatory scheme would have a substantial influence on price and market conditions. Here too, Congress had a rational basis for concluding that leaving homeconsumed marijuana outside federal control would similarly affect price and market conditions.
Slip op. at 16. More to the point:
In assessing the scope of Congress authority under the Commerce Clause, we stress that the task before us is a modest one. We need not determine whether respondents activities, taken in the aggregate, substantially affect interstate commerce in fact, but only whether a rational basis exists for so concluding.
Id. at 19. Justice Scalia agreed:
I thus agree with the Court that, however the class of regulated activities is subdivided, Congress could reasonably conclude that its objective of prohibiting marijuana from the interstate market could be undercut if those activities were excepted from its general scheme of regulation. See Lopez, 514 U. S., at 561. That is sufficient to authorize the application of the CSA to respondents.
Scalia's concurring opinion at 10.