After voters in Colorado and Washington approved the legalization of marijuana last week, Justice Department spokeswoman Nanda Chitre declared that "the Department's enforcement of the Controlled Substances Act remains unchanged." If so, the feds will treat state-legal sales of marijuana for recreational use the same way they have treated state-legal sales of marijuana for medical use: with periodic raids, threats of forfeiture and prosecution, and various other forms of harassment that fall far short of closing down all the cannabis outlets. But the Obama administration also could try to avoid that embarrassing outcome through litigation aimed at preventing Colorado and Washington from implementing their plans to license and regulate the production and sale of marijuana.

In an interview with Politico, former Drug Enforcement Administration head Asa Hutchinson concedes that the federal government cannot force states to ban marijuana but argues that "you can go in and say the state does not have the authority to set up a regulatory environment." Hutchinson, who ran the DEA during George W. Bush's first term, envisions a lawsuit that will "have the courts decide finally that federal law trumps and that the state law violates the federal law." But even if we concede the validity of the Controlled Substances Act (which requires accepting an absurdly broad interpretation of the Commerce Clause), it is not clear how, exactly, the Colorado and Washington initiatives violate it.

"There are provisions in both of the initiatives that unambiguously violate federal law," claims Kevin Sabet, a former Obama administration drug policy adviser. For instance, he says, "the fact that you can buy marijuana at the store" is "clearly in violation." Well, yes, the people selling marijuana definitely are violating federal law, but that does not make the laws under which they are licensed invalid. The Controlled Substances Act (CSA) suggests otherwise:

No provision of this subchapter shall be construed as indicating an intent on the part of the Congress to occupy the field in which that provision operates, including criminal penalties, to the exclusion of any State law on the same subject matter which would otherwise be within the authority of the State, unless there is a positive conflict between that provision of this subchapter and that State law so that the two cannot consistently stand together.

According to the Supreme Court, a "positive conflict" exists "when it is impossible to comply with both state and federal law." But neither Colorado's Amendment 64 nor Washington's Initiative 502 requires anyone to grow or sell marijuana. One can readily comply with both state and federal law simply by choosing not to go into the cannabis business. Both laws are written so that they merely explain the criteria people must satisfy to avoid prosecution for marijuana offenses under state law. "Notwithstanding any other provision of law," begins the section of Amendment 64 dealing with marijuana growers and sellers, "the following acts are not unlawful and shall not be an offense under Colorado law." I-502 likewise says "the production, possession, delivery, distribution, and sale of marijuana in accordance with the provisions of this act and the rules adopted to implement and enforce it, by a validly licensed marijuana producer, shall not be a criminal or civil offense under Washington state law."

In other words, both laws define what counts as a crime under state law, a power that states indisputably have. "You're not actually creating a positive conflict with the federal [law]," says Alison Holcomb, director of the Yes on I-502 campaign, "because the federal government remains free to enforce federal law within the state, and you're not requiring anybody to perform an act that would require a violation of federal law. You're simply setting out what the rules are for avoiding arrest and prosecution under state law."

Nor does either law compel state employees to violate the Controlled Substances Act by "possessing" marijuana for regulatory purposes. Under I-502, testing of marijuana will be handled by private laboratories. Amendment 64 likewise envisions "marijuana testing facilities" that will be "licensed to analyze and certify the safety and potency of marijuana."

What about collecting tax revenue from marijuana sales? Legally, those provisions could be the most vulnerable aspects of these laws (although it looks like Colorado's pot tax may never take effect). Jonathan Caulkins, a drug policy expert at Carnegie Mellon University, tells Politico, "The argument has been made— and I've never heard anybody successfully rebut it—that the federal government can seize the proceeds of any illegal activity. By that logic, it could seize the tax revenues—even from the states." But in Marijuana Legalization: What Everyone Needs to Know, Caulkins and his three co-authors observe that although "it has been argued that the federal government could confiscate such revenues as proceeds of illegal transactions…as far as we know the federal government has not touched a penny of the fees and tax revenues generated from medical marijuana."

Likewise, as Brian Vicente, co-director of the Yes on 64 campaign, notes, the Justice Department has not used a federal pre-emption argument to challenge the licensing of medical marijuana providers by states such as Colorado, Maine, and New Jersey. "If there were a strong federal case to be brought," Vicente says, "I think it already would have happened." Holcomb says she sees the lack of federal litigation so far, despite the adoption of medical marijuana laws by 18 states (including Massachusetts, where voters approved an initiative last week), as "a hopeful sign." Since Colorado and Washington plan to implement their regulations during the next year or so, she says, there should be plenty of time to confer with federal officials and avoid a legal confrontation. "My hope would be that the [Obama] administration would choose to approach this as a policy issue, as a political issue," she says. "It's clear that nationwide public opinion is shifting quickly and dramatically on this issue….It would be more productive for the individual states, for the federal government, and for our neighbors to the north and south if we gave states leeway to try different approaches other than marijuana prohibition."