Rep. Andy Harris opposes liberalizing marijuana laws and successfully attached a budget rider to a spending bill Wednesday to block the District of Columbia from implementing laws that reduce pot possession penalties.

Democrats howled that Harris, R-Md., and fellow Republicans on the House Appropriations Committee unfairly acted to scuttle self-governance in the district, which the Constitution puts under Congress’ supervision.

But Harris says the restriction doesn’t stomp on local autonomy as much as his critics claim.

“The district can always choose not to enforce a law,” he tells U.S. News. “This is what’s so interesting about this entire discussion. The D.C police department doesn’t have to arrest people, just like they don’t have to charge someone driving 56 mph in a 55 mph zone. They don’t have to arrest someone for the possession of marijuana. The D.C. police department is choosing to do it. They could always choose not to do it on their own, they could choose not to do it now.”

That’s not something Harris wants, but it’s something he concedes local authorities have the power to do.

The Washington Post reported Wednesday that city officials are looking at the possibility Harris' amendment could prevent district police from enforcing any local law against small-time marijuana possession by virtue of blocking reduced sanctions. Older penalties would already have been repealed.

The office of the D.C. attorney general did not respond to a request for comment on its current analysis.

Harris argues district authorities could choose what penalties to apply if his amendment is put on the books.

“It would be whatever the district wanted to do,” he says. “The district could choose to enforce the federal law, it just can’t enforce a lower-penalty district law.”

Harris’ anti-decriminalization amendment was adopted in a 28-21 committee vote and would prevent the city from spending money to “enact or carry out” laws, rules or regulations that reduce marijuana penalties.

Editorial Cartoons on Marijuana View All 15 Images

The committee-approved measure is a specific reaction to a law passed by the D.C. Council in March that would reduce penalties for possession of up to 1 ounce of marijuana to a $25 civil fine, replacing misdemeanor penalties of up to six months in jail and/or a fine of $1,000. Harris' amendment would not block the law, but merely prohibit its implementation.

It’s similar to a 1998 budget rider that banned the district from allowing medical marijuana for more than a decade, until congressional Democrats allowed that prohibition to lapse in 2009. The city’s first pot dispensaries opened in July 2013.

The District of Columbia had a higher per capita arrest rate for marijuana possession than any of the 50 states in 2010, according to a 2013 American Civil Liberties Union report. More than 90 percent of those arrested were black. The racial enforcement disparity is one of the primary reasons cited by city politicians who support reducing penalties.

Harris says the dramatic reduction of penalties, however, inspired his passionate opposition. He says teens are more likely to use marijuana if the consequence is a slap on the wrist.

Harris’ amendment would also block any attempt to legalize and regulate marijuana in the district. Activists are likely to submit enough petition signatures next month to put legalization on the November ballot. Polls show city residents broadly support outright legalization.

The amendment must survive a possible House floor fight and then pass the Senate and/or emerge from a Senate-House conference committee before the underlying spending bill goes to President Barack Obama for his signature.

The district decriminalization law is likely to take effect on or around July 17 and before that would happen.

Harris says he’s confident that any floor fight would end in his favor, even though the House voted 219-189 on May 30 to ban the Department of Justice – including the Drug Enforcement Administration and federal prosecutors – from going after medical marijuana in states that allow it.