D.C. VOTERS, as expected, gave overwhelming approval to a ballot initiative that would legalize marijuana and, as expected, there were immediate rumblings from Capitol Hill of plans to block its implementation. We did not favor passage of Initiative 71, but we do believe in democracy and self-government. Congress should recognize how inappropriate it would be to interfere with the District on this local issue.

Within hours of Tuesday’s passage of a measure that would make it permissible for adults in the District to possess as much as 2 ounces of marijuana, Rep. Andy Harris (R-Md.) signaled his interest in preventing the law from going into effect. “I will consider using all resources available to a member of Congress to stop this action,” said Mr. Harris, who previously tried to upend the District’s decriminalization of marijuana. Mr. Harris said his interest stems from concerns about the possible impact of legalization on adolescent drug use, yet he has shown little interest in the welfare of teenagers who reside in states that have moved to legalize the drug.

The District, because of its unique relation to Congress, is an easy stalking horse for members to advance agendas that would be unpalatable in most jurisdictions. And the Democratic-majority city’s always-tenuous relationship with the Hill became even more precarious with the Republican sweep of the midterm elections.

There are, nonetheless, some hopeful signs that Congress might respect D.C. rights on this matter. The GOP-controlled House went on record this year as opposing the use of funds to prevent states from implementing laws that authorize the use, distribution and possession of medical marijuana. Rand Paul (Ky.), the ranking Republican on the Senate committee with oversight of the District, has said that D.C. voters, not Congress, should decide this issue. “I’m not for having the federal government get involved,” he told Roll Call.

That Congress will scrutinize the law is all the more reason the District needs to take care in crafting a system that regulates the sale of the drug. The experience of states such as Colorado have revealed unintended — and harmful — consequences, most notably problems with marijuana’s main active ingredient in food products. The D.C. Council, which did a good job establishing rules for medical marijuana, should do its homework on how legalization is unfolding in other states before allowing Initiative 71 to go into effect.