At the outset, this seems like a major blow for the fight to legalize marijuana. Who (or what) has the most to lose?

Science. Perhaps most notable about the decision, even taking into account the DEA's careful language, is that it attacks the popular belief that the medical benefits of marijuana are long established. Synthetic forms of marijuana, for one, are federally approved in treating conditions like glaucoma. Neuropsychiatrist Dr. Igor Grant, director of the Center for Medicinal Cannabis Research at UC San Diego, told the LA Times that state-supported clinical trials show that marijuana helps with neuropathic pain and muscle spasticity. Joe Elford, chief counsel for Americans for Safe Access, noted that studies demonstrate pot stimulates the appetite for people undergoing chemotherapy. But more research needs to be done. In 2009, the American Medical Assn. urged the government to review its classification of marijuana "with the goal of facilitating the conduct of clinical research and development of cannabinoid-based medicines, and alternate delivery methods." Thus, there is fear that this latest ruling may hinder medical research for some time to come.

State law. When the petition was originally filed, eight states had approved medical marijuana. Now 16 states and the District of Columbia have joined in. Will users of medical marijuana continue to be protected by their states' laws? That issue is also becoming less clear. In the recent past, the federal stance on marijuana was not a threat to legal users under state law. In an October 2009 memo to U.S. attorneys, Deputy Attorney General David Ogden instructed that they "should not focus federal resources" on "individuals whose actions are in clear and unambiguous compliance with existing state laws providing for the medical use of marijuana." But late last month Ogden's successor James Cole issued a new policy that "commercial operations cultivating, selling or distributing marijuana" are, in the words of Jacob Sullman at Reason, "fair game, even when they are explicitly authorized by state law." Sullman describes:

The new memo even suggests that state employees could be prosecuted for licensing and regulating dispensaries, saying people "who knowingly facilitate" the distribution of medical marijuana "are in violation of the Controlled Substances Act, regardless of state law," and "are subject to federal enforcement action, including potential prosecution."

In light of this recent finding by the DEA, the federal government has only strengthened its disparate position from many states.

Federal law. On a federal level, however, this ruling is not all bad news for marijuana advocates. According to chief counsel Elford, the government was employing a "strategy of delay" these past nine years, and, now that it has come out on one side, advocates can finally appeal, enabling them to "go head-to-head on the merits." However, it should be noted that the two times when petitions to reclassify marijuana failed in the past, first in 1972 and then in 1995, the courts sided with the federal government on the appeal.