Justice Stevens wrote for the majority, "Congress can regulate purely intrastate activity ... if it concludes that failure to regulate that class of activity would undercut the regulation of the interstate market in that commodity."
Justice Scalia wrote in his concurrence, "... the commerce power permits Congress ... to facilitate interstate commerce by eliminating potential obstructions, and to restrict it by eliminating potential stimulants."
Wordy prose, to be sure, but no different from what I said.