Two weeks ago, nearly 10 months after voters in Colorado and Washington decided to legalize marijuana, the U.S. Justice Department finally responded. Its announcement, which took the form of a memo to U.S. attorneys from Deputy Attorney General James Cole, promised neither acceptance nor confrontation, saying only that the Justice Department probably has better things to do than prosecute newly legal marijuana growers and sellers, provided state regulation is strict enough to allay federal concerns.

This conditional forbearance was widely interpreted as a "green light" for legalization. But anyone familiar with the Obama administration's inconsistent, disingenuous approach to medical marijuana has to wonder whether the Cole memo truly signals a newfound respect for state policy choices.

Cole listed eight "enforcement priorities" that Colorado, Washington, and the 18 states where marijuana is legal for medical but not recreational use will be expected to address. The three most significant probably are "preventing the distribution of marijuana to minors," "preventing the diversion of marijuana from states where it is legal under state law in some form to other states," and "preventing drugged driving and the exacerbation of other adverse public health consequences associated with marijuana use." But the list also includes "preventing the growing of marijuana on public lands," "preventing marijuana possession or use on federal property," "preventing revenue from the sale of marijuana from going to criminal enterprises," "preventing violence and the use of firearms in the cultivation and distribution of marijuana," and "preventing state-authorized marijuana activity from being used as a cover or pretext for the trafficking of other illegal drugs."

If a state fails to adequately deal with these issues, Cole said, the Justice Department may yet decide to prosecute state-approved suppliers or "challenge the regulatory structure itself." This exercise of prosecutorial discretion is completely one-sided, subject to suspension at any time. Not only can the Justice Department change its policy at will; it is the sole interpreter of these eight goals and the sole judge of whether states are doing enough to reach them. Just to give you a sense of the ambiguity and subjectivity inherent in Cole's criteria, the feds could say all bets are off if campers in national parks are caught smoking pot, if a 22-year-old buys marijuana at a state-licensed store and shares it with his 20-year-old brother, if pot shop owners exercise their Second Amendment rights by keeping guns for self-protection, or even if cannabusinesses make money, since all of them are "criminal enterprises" under federal law.

Further grounds for skepticism can be found in two earlier Justice Department memos that Cole mentions. The first, issued in October 2009 by Cole's predecessor, David Ogden, seemed to fulfill promises by President Obama and Attorney General Eric Holder that the Justice Department would not try to undermine state medical marijuana laws by targeting suppliers who comply with them. Ogden told U.S. attorneys that "as a general matter" 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." He listed criteria for federal prosecution, such as "sales to minors," "sale of other controlled substances," and "financial and marketing activities" inconsistent with state law, that made sense only when applied to suppliers, which jibed with what Obama and Holder had repeatedly said.

The Ogden memo inspired a "green rush" of cannabis entrepreneurs in states with medical marijuana laws, provoking outrage among federal drug warriors, who launched a crackdown more aggressive than anything seen under George W. Bush. In June 2011, seeking to retroactively justify these raids, seizures, and arrests, Cole issued a memo falsely claiming that the Justice Department's policy of forbearance had always been limited to patients and their caregivers. According to Cole's gloss, the feds never imagined that people would make money by supplying patients with marijuana, even though the Ogden memo clearly contemplated that prospect. Given Cole's willingness to lie about the policy he was contradicting and Holder's willingness to bless that lie, even while continuing to promise tolerance of medical marijuana dispensaries, the latest memo has to be taken with a shakerful of salt.

As Tom Angell, chairman of Marijuana Majority, puts it, "My optimism is tempered by the fact that despite the Justice Department's 2009 announcement that it shouldn't be a priority to bust medical marijuana providers operating in accordance with state law, this administration went on to close down more state-legal marijuana businesses in one term than the Bush administration did in two terms." Fool me once…

This article originally appeared at Forbes.