Allen St. Pierre of the National Organization for the Reform of Marijuana Laws calls that stance "hyperbolic." "The previous ten presidents did nothing," he says. Obama has "taken the federal hand off the scale a wee bit."'

Most notably, the Veterans Administration and the Department of Housing and Urban Development have revised regulations to acknowledge the use of medical marijuana.

For example, although federal zero-tolerance laws prohibit illegal-drug users from living in public housing or receiving rent subsidies such as Section 8, HUD has given local housing authorities in states that allow medical marijuana the discretion to not evict users.

Still, St. Pierre worries that the combination of raids and IRS harassment is seriously endangering medical marijuana. An unfavorable court decision regarding the IRS audits "could end medical cannabis," he warns. "They're going the Al Capone route."

The VA is the bright spot, says Michael Krawitz of Veterans for Medical Cannabis Access. Although it still forbids its doctors from recommending marijuana, and possession is illegal on VA property, last year it changed its regulations so that medical-marijuana use is no longer an automatic violation of "pain contracts"-agreements patients sign in which they state that they're not going to abuse their prescription painkillers.