Matt Franck takes a whack not only at Obama's decriminalization policy but at some conservative defenders of it who see a respect for federalism:
By announcing the non-prosecution of marijuana cases only in those 14 states that legalize some use of the drug for medical purposes, the administration has effectively proclaimed that federal law means one thing in those 14 states, and something else in the other 36. That could readily give rise to equal protection claims in the 36 states where the federal government still considers itself free to prosecute.
Moreover: "Worse, by conditioning the prospect of prosecution on the presence or absence of state laws that contradict a nationwide federal prohibition, the Justice Department has effectively subjected the validity of federal law to the will of state legislators." As a prelude to relaxing drug prosecution generally, "This way evinces Professor Obama's usual respect for the Constitution: he rolls his own."