At last, some common sense about medical marijuana, and from the federal government, no less. Unlike its interventionist predecessor, the Obama administration has decided to be conservative about this controversial issue, and leave state business to the states.

We don’t know that California and the other states that have legalized marijuana for medical use as a pain reliever have done the right thing, but we always found it odd that the putatively conservative Bush administration insisted on thrashing around in a matter that was not its business. The Constitution leaves matters like that to the states, and the conservative approach would be to hew to the Constitution.

That’s what the Obama administration has done, and for reasons even more convincing than constitutional cleanliness. After months of review, the Justice Department recently concluded that federal prosecutors and drug agents have better things to do than to chase pot smokers who are following the laws of states that allow some use of medical marijuana. Oh, right: People are still trying to kill Americans by the thousands. We should be chasing them, as well as violent Mexican drug cartels that use their American profits to finance other criminal activities.

Some 13 states—New York is not among them—allow for some use of medical marijuana. Some have been reluctant to implement the programs they passed for fear of federal intrusion.

Times change. As an op-ed piece recently pointed out on this page, depictions of marijuana use are becoming commonplace on television and in movies. For better or worse, no one seems to care much. Allowing the states to test the advisability of legalizing medical marijuana, known to ease suffering in cases where other agents fail, doesn’t seem radical at this point. Indeed, it is the concept of federalism at work, if in a different way than anyone would have imagined a generation ago.

With this change, states will be able to use the authority that belongs to them. The federal government will have to divert fewer hours in pursuit of a policy whose pointlessness is underscored by the real challenges federal law enforcement must confront. And people who are suffering may find a measure of relief without worrying about criminal charges.

In the meantime, science needs to continue to evaluate the uses of medical marijuana and perhaps even to seek more effective substitutes. The point isn’t a back-door legalization of pot, but relieving pain which, to most of us, is unimagineable.