There are a lot of caveats. The Justice Department included a long list of demands that those states must meet in order to avoid federal intervention. Advocates quickly point out the Obama administration's previous assurances that it wouldn't interfere with medical marijuana hasn't stopped federal agents from raiding operations that they say conflict with federal and state laws. How individual U.S. attorneys react will be crucial -- one in Washington actually alleged after the announcement that her state's medical marijuana system violated the new guidance.
But it's still a big deal. This is the federal government acknowledging that, within a specific set of parameters, a Schedule I narcotic under the 1978 Controlled Substances Act (effectively the legal foundation for the War) can be fully legalized. That's a complete reversal of federal policy since 1971, when President Richard Nixon first declared war on drugs.
"This is a big deal. This really is a dramatic departure from the earlier enforcement of state marijuana laws," Robert Mikos, a law professor at Vanderbilt University, told TPM. "It could portend larger changes with respect to the war on marijuana. It could also embolden legalization efforts in a lot more states. That could end up being the biggest ramifications, that political shift."
Last week, a poll found that 82 percent of Americans believe the nation is losing the War on Drugs. That same poll found a majority agreed with a decision by Attorney General Eric Holder to reduce the number of mandatory minimum sentences for drug convictions, another important shift in federal policy. It reflects a belief among advocates, one endorsed by the White House itself, that drug addiction should be viewed more as a public health issue than a criminal one. In their mind, that's the end game for the War.
Others were more tempered in their response. Mark Kleiman, a public policy professor at UCLA who focuses on drug policy, said that the memo was effectively what he was expecting. It still leaves enforcement decisions to the discretion of individual officials -- as the Washington U.S. attorney's pronouncement reinforced -- and there's enough rhetorical wiggle room for federal agents that businesses and users could still be targeted for prosecution.
"The (November 2012 voter) initiatives mark an epoch in drug policy reform, and it seems to me that this is a modest accommodation," Kleiman told TPM. "But they are making it clear that they respect state enforcement systems. That's a big deal."
Advocates, for their part, were jubilant, seizing the announcement as a historical shift in federal policy.
"The war on drugs I would expect will end today," Terry Nelson, a retired U.S. customs and border protection agent who now works with Law Enforcement Against Prohibition, which supports legalization, told TPM in a phone interview. "Once the floodgates open, and states see that the federal government is not going to prosecute, then this could be the day that we could say we won this war."
It should be noted that the Justice Department's pronouncement represented a fundamental change in how the federal government approaches marijuana only -- the trafficking of harder drugs like heroin and cocaine will still likely be as vigorously prosecuted as they are now. But even on those drugs, Holder's sentencing guidance represents a recent reevaluation in how the federal government views its role.
The changes in marijuana policy are seismic, though, Vanderbilt's Mikos said. The Justice Department named very narrow interests in which it wants to crack down on marijuana: keeping it out of the hands of minors, stopping it from crossing state borders and preventing marijuana sales from funding other criminal activity. As importantly, the federal government acknowledged that there could be legal forms of marijuana trafficking, as long it complies with state regulations.
Recent polling has started to routinely show that a slim majority of Americans support marijuana legalization. Thursday's announcement could encourage that movement. The Marijuana Policy Project, one of the major policy organizations on the topic, has set its sights on legalization in Rhode Island, Alaska, Oregon, Maine and California in the next year.
There are also those who warn that the Justice Department is a fundamental mistake, rife with potential for unintended consequences. But even they agreed with its historical significance.
"This President will be remembered for many failures, but none as large as this one, which will lead to massive youth drug use, destruction of community values, increased addiction and crime rates," Paul Chabot, a drug policy advisor for the Clinton and Bush White Houses, wrote to TPM in an email. "America may never recover."