Complex sentence: The U.S. Supreme Court disagreed, reasoning that cannabis grown within California for medical purposes is indistinguishable from illicit marijuana and that because the intrastate medical cannabis market contributes to the interstate illicit marijuana market, the Commerce Clause applies.
Split into simpler sentences: The U.S. Supreme Court disagreed, finding that cannabis grown within California for medical purposes is indistinguishable from illicit marijuana. Moreover, because the intrastate medical cannabis market contributes to the interstate illicit marijuana market, the Commerce Clause applies.