It had all the markings of a measure that would no one notice: an obscure amendment to a low-profile bill, receiving a vote after midnight, the same week as a national holiday. It’s hardly a recipe for generating national headlines.

But the U.S. House of Representatives nevertheless did something overnight that Congress has never done

The House passed an amendment late Thursday night to restrict the Drug Enforcement Administration from targeting medical marijuana operations in states where it is legal. The 219-189 decision came on a bipartisan appropriations amendment spearheaded by California Republican Rep. Dana Rohrabacher and California Democrat Sam Farr. The amendment still faces several procedural hurdles before it is ratified, but this is the first time such an amendment has succeeded in the House.

The roll call on the vote is here . Note that it passed largely with Democratic support – the vast majority of Dems voted for it; a clear majority of Republicans voted against it – but the measure was backed by a bipartisan group of co-sponsors.

At issue is a routine spending bill: providing federal funding for a variety of agencies, including the Justice Department, which occasionally enforces federal drug laws by raiding marijuana facilities in states where medical pot sales are legal.

The amendment intends to block federal law enforcement from doing so in the future.

In the process, as German Lopez reported , the House acted without precedent: “The bill is the first time in history that any chamber of Congress has acted to protect medical marijuana businesses and users.”

As Lopez’s report makes clear, the practical effect of the amendment means the House now believes that if states want to implement their own medical marijuana laws, they shouldn’t have to fear interference from the FBI.

“Congress is officially pulling out of the war on medical marijuana patients and providers. Federal tax dollars will no longer be wasted arresting seriously ill medical marijuana patients and those who provide to them,” Dan Riffle, director of federal policies at the Marijuana Policy Project, said in a statement. “This is a historic vote, and it’s yet another sign that our federal government is shifting toward a more sensible marijuana policy.”

Looking ahead, it’s not yet a done deal. The same spending bill has not yet been taken up by the Senate, and we don’t yet know how the upper chamber will feel about the DEA amendment. The measure would also need President Obama’s signature.