Mary Jane’s Last Dance?

Dahlia Lithwick has a snarky look at the Supreme Court’s oral arguments concerning California�s medical marijuana law, asking �should the court’s staunchest conservatives get away with being for states’ rights only when the state in question isn’t California?
I�m sympathetic to the medical marijuana law in question, defended in this case by Randy Barnett, and, in fact, would support a good deal of reform of American drug laws. Yet Lithwick�s accusations of hypocrisy would be a lot more convincing if the Court had not, on the very same day, (correctly) declined to hear a case challenging the Massachusetts Supreme Court�s (egregious) �gay marriage� ruling, presumably on federalism grounds.
Also, in a broader sense, this is an annoying form of argument. One gets the sense here that Lithwick doesn�t really believe in federalism, but supports using it as a justification for drug legalization at the state level. Isn�t that line of reasoning just as hypocritical as that which she prematurely accuses the Supreme Court of following?