The House on Wednesday voted to continue to allow federal prosecution of those who smoke marijuana for medical purposes in states with laws that permit it.
A year ago, the Supreme Court ruled that the federal government can prosecute medical marijuana users, even when state laws allow doctor-prescribed use of the drug.
By a 259-163 vote, the House again turned down an amendment that would have blocked the Justice Department from prosecuting people in the 11 states with such medical marijuana laws.
Advocates say medical marijuana use is the only way that many chronically ill people, such as AIDS and cancer patients, can relieve their symptoms.
The vote came as the House debated a $59.8 billion bill covering the departments of Commerce, Justice and State.
"If the voters have seen to it and a doctor agrees, it's a travesty for the government to intercede ... to get in the way of someone using something to alleviate their suffering," said Rep. Dana Rohrabacher, R-Calif. "This is something that should be left to the states as American tradition dictates."
"Marijuana is not harmless as some claim," said Rep. Tom Latham, R-Iowa. "Marijuana continues to be the most widely abused drug in the United States."
Opponents of the amendment said Marinol, a government-approved prescription drug that contains the active ingredient in marijuana, offers comparable relief for pain and nausea.
Eight states — Alaska, California, Colorado, Maine, Montana, Nevada, Oregon and Washington — have legalized medical marijuana by voter referendums. The legislatures of three others — Hawaii, Rhode Island and Vermont — have legalized the practice. All require a doctor's approval.