The truth is that the federal ban on marijuana -- unlike the federal ban on alcohol, which began and ended with constitutional amendments -- has no basis in the powers granted by the Constitution, at least insofar as it purports to reach purely intrastate activities. But as a politician who routinely relies on the Commerce Clause to justify his initiatives (including his signature legislative accomplishment), Obama will never admit that.
Still, if Obama truly believes "it's important" that states have the leeway to try different approaches to marijuana, why not codify that policy? The Respect State Marijuana Laws Act, introduced last spring by Rep. Dana Rohrabacher, R-Calif., would do just that by declaring that the provisions of the Controlled Substances Act dealing with cannabis "shall not apply to any person acting in compliance with state laws."
By supporting this bill, Obama could show he is serious about letting states go their own way on marijuana without abandoning his broad view of the federal government's powers. Republicans could appeal to younger voters -- two-thirds of whom support legalization, according to a 2013 Gallup poll -- while remaining faithful to a principle they claim to uphold.
Several recent surveys indicate that most Americans favor legalization, while even larger majorities say the federal government should not interfere with legalization at the state level. We seem to have the makings of a national consensus on this issue: We do not need a national consensus.