The Treasury guidance was intended to give banks confidence that they can deal with marijuana businesses in states where they're legal. Many banks are still reluctant to do so.
That has forced many marijuana operations to stockpile cash, a situation that shop owners say is dangerous.
"They are operating just in cash, which creates its own potential for crime, robbery, assault and battery," said Rep. Ed Perlmutter, D-Colo., whose state has legalized recreational pot use. "You cannot track the money. There is skimming and tax evasion. So the guidance by the Justice Department and the guidance by the Treasury Department is to bring this out into the open."
The vote is largely symbolic since Treasury already had gone ahead with the guidance, but it demonstrates a loosening of anti-marijuana sentiment on Capitol Hill.
"Whereas the federal government once stood in the way of marijuana reform at every opportunity, the changing politics of this issue are such that more politicians are now working to accommodate popular state laws so that they can be implemented effectively," said marijuana advocate Tom Angell.
A coalition of 46 mostly GOP moderates and libertarian-tilting Republicans joined with all but seven Democrats to beat back Fleming's attempt to block the Treasury guidance.
The underlying measure, however, would block the District of Columbia from implementing a local law decriminalizing pot possession. The D.C. City Council approved a measure reducing the penalty for possession of up to an ounce of marijuana to a $25 fine.
That provision, by Rep. Andy Harris, R-Md., also would block the city from legalizing pot as Colorado and Washington state have done.