Marijuana – smoking it, eating it, growing it in modest amounts — is legal. To even be writing those words is historic. But don’t light up just yet. The new pot laws passed in state referendums Tuesday night only apply to Colorado and Washington, and as far as the feds are concerned, smoking pot is still a criminal offense and a critical threat in the decades-long War on Drugs.

But enough of the buzz kill. There have been small steps toward ending marijuana prohibition — state medical-marijuana laws being the most radical — in the last several years. Recently the tide has turned against draconian laws that have sent pot offenders to prison while drug smugglers and gangs thrive off the black market. Thus more mainstream attention and credibility has been given to plans like the ones passed Tuesday that would regulate, tax, and sell marijuana to adults, just like alcohol, in both Colorado and Washington.

If not for establishment support, including from government figures, law enforcement and the medical community, these measures would never have passed. A medical-marijuana initiative in Arkansas and a legalization plan in Oregon did not pass last night because they did not have the same kind of support.

What does this all mean? First off, Colorado and Washington have a lot of work to do to establish the infrastructure to make this happen (the state of Colorado, by the way, hopes to make anywhere from $5 million to $22 million yearly by taxing marijuana sales).

Next, as Jordan Bloom pointed out last week, a federal standoff — a constitutional standoff – may be inevitable. Allen St. Pierre, head of the National Organization to Reform Marijuana Laws (NORML), predicts it will play out in the courts. Likely it will play out in the streets, too. The federal government has been adamant that marijuana is a dangerous drug and under the Obama Administration has taken to stepping up raids against medical-marijuana distributors in California and Colorado to prove it.

Bloom reminds that the Obama administration actually suggested it would stand-down on medical marijuana when President Obama took office in 2008. But that didn’t last long, taking by surprise advocates who thought Obama was on their side. That scenario could happen again:

Consider this hypothetical situation … All of a sudden the DEA starts knocking down doors in Denver or Seattle. But the targets, unlike in California (where there have been more than 800 raids this year) or other medical marijuana states, will not just be dispensaries, but an array of businesses that also sell other things. The governors will be under immense pressure to act to enforce the laws they were elected to uphold. Such action could range from publicly condemning the raids to throwing federal agents in prison: full-on nullification. That’s the “constitutional showdown” the Justice Department has warned us about.

How far states will have to go to exercise self-government depends above all on the intractability of the DEA. I have no doubt that if it actually came down to states arresting DEA agents the federal government would be forced to reevaluate. Doubling down would mean arresting the governor or invading, and that seems exceedingly unlikely.

However the story may end, for now marijuana-reform advocates have reason for optimism.