On Thursday, the Justice Department issued its long-awaited reaction to the decisions by Washington and Colorado voters to legalize marijuana for recreational use. The verdict: Marijuana is still illegal under federal law, but the feds will essentially stand back and let states continue their pot experiments, at least for now.

It's a big deal that the Justice Department didn't file suit to stop states from setting up a regulated, legal marijuana market. Now, weed proponents will get their chance to "show that legalizing pot is better, less costly, and more humane than the last 75 years of prohibition — all with the federal government's blessing," say the AP's Gene Johnson and Pete Yost.

This is "nothing short of historic," Dan Riffle of the Marijuana Policy Project tells the AP. "It's a very big deal for the DOJ to say that if the states want to legalize marijuana, that's fine. Everybody in this movement should be thrilled."

There is a catch, of course: If the states that legalize pot fail to keep it away from kids, out of the hands of cartels, off the black market, and away from other states and federal lands, the feds will step in and crack down. Also, individual federal prosecutors will have some discretion to ignore the new, more-lenient guidance from the Justice Department. And since it's not a change in law, another administration — or even Obama — could change the rules without warning.

But if the federal government is signaling that it will respect state laws on recreational marijuana, can't any state follow Colorado and Washington's leads? Is President Obama really "evolving" on legalizing pot?

Proponents are cautiously optimistic. "The war on drugs may have ended today," says Maia Szalavitz at TIME. The DOJ's decision has broad implications for the nation as a whole, affecting what other states decide and how legislators look at drug enforcement and regulation. "It reflects the first profound crack in the federal edifice of drug prohibition since President Nixon first declared war on drugs in 1971," says Szalavitz.

And as pioneering as it seems, the decision actually has precedent — in the end of alcohol Prohibition back in the 1920s and 1930s.... A decade before Prohibition was repealed in 1933, New York state passed a law eliminating funding for enforcement, which essentially re-legalized alcohol sales there. The fact that the federal government appears to be backing off — rather than cracking down — on marijuana use and sales could reflect a similar turning point in marijuana prohibition. [TIME]

Not everyone is convinced that Thursday's announcement is really that big a deal. It's worth remembering that "for some time now Barack Obama's administration has been saying nice things about ending the war on drugs while continuing to enforce viciously unjust prohibitionist laws," says Harry Cheadle at Vice. So we'll see how serious the feds take this stated policy shift. What seem clear is that the obvious solution — "legalizing weed at the federal level" — is "still impossible politically" for the foreseeable future. Here's the bottom line:

Just like the feds are going to wait and see how the regulation of legal marijuana works out, drug-war doves are going to have to wait and see if agencies like the DEA and the FBI, who have been sending pot dealers to jail since J. Edgar Hoover was in panty hose, will really allow cannabis to be bought and sold in massive quantities. Likely, it really will depend on how strict the regulations are: The feds are fond of raiding medical marijuana clinics in California, where there's a lot of conflicting local laws and it's often not clear where the pot comes from; Colorado's dispensaries, however, electronically track every gram sold and have been largely left alone. [Vice]

Reason's Jacob Sullum — who falls squarely in the legalize-it camp — is also skeptical, but takes heart from the fact that pot prohibitionists hate the new policy. He cites Kevin Sabet, a former Office of National Drug Control Policy staffer, who calls the decision "disappointing" and predicts that "this will quicken the realization among people that more marijuana is never good for any community." But other marijuana opponents are harsher.

Attorney General Eric Holder, in not enforcing federal law over state law, is "not only abandoning the law, he's breaking the law," former DEA chief Peter Bensiger tells the AP. The lax drug policy "sends the wrong message to both law enforcement and violators of federal law," agrees Sen. Charles Grassley (R-Neb.). "Apprehending and prosecuting illegal drug traffickers should always be a priority for the Department of Justice."

If there's one thing both sides of the marijuana debate can agree on, it's that Thursday's decision will encourage other states to start their own legalization experiments. Efforts to follow in Washington and Colorado's footprints are already underway in Oregon, Nevada, Massachusetts, and Alaska.

So pot isn't really legal in the U.S. today, but it's a good deal less illegal. The last word goes to Ethan Nadelmann at the Drug Policy Alliance, which advocates reforming marijuana laws:

Today's announcement demonstrates the sort of political vision and foresight from the White House we've been seeking for a long time.... I must admit, I was expecting a yellow light from the White House. But this light looks a lot more green-ish than I had hoped. The White House is basically saying to Washington and Colorado: Proceed with caution. [Drug Policy Alliance]