Other cosponsors of the bill include Rep. John Conyers (D-MI), Rep. Steve Cohen (D-TN), Rep. Jared Polis (D-CO), and Rep. Barbara Lee (D-CA). The legislation would limit the federal government's role in marijuana enforcement to cross-border or interstate smuggling, allowing people to legally grow, use or sell marijuana in states where it is legal.

The bill does not reschedule marijuana, which is currently Schedule I, the most serious classification under the Controlled Substances Act; it removes it from the act altogether.

"We are introducing a bill today that is very straightforward," said sponsor Rep. Barney Frank (D-MA) at a Capitol Hill press conference Thursday afternoon. "We do not believe the federal government ought to be involved in prosecuting adults for smoking marijuana. That is something the states can handle. We have this problem where those states that want to reform their marijuana laws are prevented from doing so by the federal government. Under this bill, the federal government will concentrate its prosecutorial resources on other things and respect any decision by a state to make marijuana legal," the veteran congressman said.

"We're very excited about promoting a new, sensible approach to marijuana," said Rep. Polis. "We can set up a proper regulatory system, as Colorado has done. It would be wonderful for the federal government to let states experiment. Our current failed drug policy hasn't worked -- marijuana is widely available. By regulating the market, we can protect minors and remove the criminal element so we can focus law enforcement resources on keeping people safe in their communities."

"This has long been an issue of freedom for me," Rep. Cohen told the press conference. "The people are way ahead of the legislators in knowing what the priorities of law enforcement ought to be. The federal government shouldn't be spending its time and money on marijuana, but on crack, meth, heroin, and cocaine. It ought to be up to the states and regulated like alcohol. It should be a matter of individual choice in a country that prides itself on its liberties and freedoms."

The timing for the introduction of the bill is exquisite. Just days earlier, people marked the 40th anniversary of President Richard Nixon's declaration of the war on drugs with protests and vigils around the country. Earlier this month, the Global Commission on Drug Policy released its report calling for a radical shift in how we deal with illegal drugs, including calling for the legal regulation of marijuana.

The introduction of the bill also comes as activists in at least four states -- California, Colorado, Oregon, and Washington -- are working to put marijuana legalization initiatives on the ballot for 2012. In the case of Washington, there are now two competing legalization initiatives, one aimed at 2011 and one at 2012.

And it comes as legalization becomes an increasingly hot topic in state legislatures. In the past year at least five state legislatures have considered legalizing marijuana, including California, Maine, Massachusetts, Rhode Island, and Washington.

It also comes as the battle between the federal government and states with medical marijuana laws is heating up. Despite the famous Justice Department memo of October 2009, which directed US attorneys to not focus prosecutorial resources on producers and providers in compliance with state laws, the Obama administration is conducting raids at a higher rate than the Bush administration, and US attorneys have recently been on a threat offensive, warning state elected officials their employees could be at risk if they approve the regulation and distribution of medical marijuana.

But while the timing is good, Frank was quick to caution that the bill was unlikely to pass Congress this session. "I don't expect it to pass right away, but given this Congress, I don't expect much good legislation to pass at all," he said. "I think we're making good progress, and the public is ahead of the politicians on this. There is an educational process going on."

Still, that dose of political realism didn't stop advocates, some of whom have been working on the issue for decades, from feeling just a little bit giddy. After all, it is an historic occasion for reformers.

"Adults who use marijuana responsibly should not be treated like criminals," said Allen St. Pierre, executive director of NORML. "Marijuana smoking is relatively harmless, is not an act of moral turpitude, and should not be treated as a crime. As a marijuana consumer myself, I've never seen my responsible use of marijuana as a crime."

Noting some 22 million arrests of otherwise law-abiding pot smokers since the 1960s, St. Pierre called for the end of pot prohibition. "Policymakers should recognize the benefits of legally controlling and taxing marijuana," he said. "We need to stop arresting millions of people who use marijuana."

"We're so proud to be standing with these members of Congress in announcing this bill to treat alcohol similarly to marijuana," said Aaron Houston, executive director of Students for Sensible Drug Policy. "A state-based approach to marijuana should be appealing to Republicans. Most people don't know that for decades after the repeal of Prohibition, many states continued to ban alcohol. With this bill, states could continue to ban marijuana, or they could regulate it if they like. This is also an issue that drives young people to the polls, and that's a huge opportunity for politicians."

"This bill is actually the ultimate bill we've been looking for at the federal level," said Rob Kampia, executive director of the Marijuana Policy Project. "If and when it passes, I expect to close our offices in DC and concentrate on working at the state level. This bill would address some of the stuff we've been hearing about from federal prosecutors threatening state governors and legislators about medical marijuana. If this passes, all the huffing and puffing form US attorneys will evaporate into thin air," he added. "And this bill will have a positive impact on ballot initiatives in California and Colorado in 2012. In the past, opponents said these initiatives wouldn't do anything because the federal government wouldn't touch the issue. Now, we can say the federal government is looking at the issue, and some of the most credible members of Congress are cosponsors."

"Last week marked the 40th anniversary of the failed war on drugs, so this is very timely, and it comes on the heels of the report by the Global Commission," said Bill Piper, national affairs director for the Drug Policy Alliance. "This is a major step toward restoring some sanity and science to our nation's drug policies. There is a growth in recognition among both voters and elected officials that marijuana legalization is not a question of if, but when. The reality is that the war on marijuana is unsustainable -- we're heading toward a perfect storm for this."

Now, marijuana legalization is before Congress for the first time since it was outlawed in 1937. While passage this session is extremely unlikely, this is indeed a step forward.

Update:  After this article was first published Thursday afternoon, reaction from a key congressional committee chair and the White House Office on National Drug Control Policy (ONDCP) made it clear that "extremely unlikely" was optimistic.

The bill would have to pass through the House Judiciary Committee, but committee chair Rep. Lamar Smith told the Associated Press there was no way that was going to happen.

"Marijuana use and distribution is prohibited under federal law because it has a high potential for abuse and does not have an accepted medical use in the US," Smith said. "The Food and Drug Administration has not approved smoked marijuana for any condition or disease."

Then he bizarrely claimed legalizing marijuana in the US would help Mexican drug cartels. "Decriminalizing marijuana will only lead to millions more Americans becoming addicted to drugs and greater profits for drug cartels who fund violence along the US-Mexico border. Allowing states to determine their own marijuana policy flies in the face of Supreme Court precedent," he threw in for good measure.

Echoing Smith, ONDCP told the Los Angeles Times legalizing weed was a non-starter. "Our concern with marijuana is not borne out of any culture war or drug war mentality, but out of what the science tells us about the drug's effects. The facts are that marijuana potency has tripled in the past 20 years and teens are using the drug at earlier ages," it said in a statement.

"The earlier a person begins to use drugs, the more likely they are to progress to more serious abuse and addiction --- reflecting the harmful, long-lasting effects drugs can have on the developing brain. Legalization remains a nonstarter in the Obama administration because research shows that marijuana use is associated with voluntary treatment admissions, fatal drugged driving accidents and emergency room admissions," the statement said.

If not this year, maybe next year. If not this Congress, maybe the next one. If not this administration, maybe the next one. There are many obstacles on the path to legalization, but now we are at least on the path.