District leaders lambasted congressional Republicans Thursday for proposing to undermine a vast swath of city gun laws, making a case that their efforts would make the nation’s capital less safe while their chief antagonist, a lawmaker from Kentucky, watched.

Rep. Thomas Massie (R-Ky.) briefly attended the Capitol Hill news conference called in response to his amendment to the D.C. budget, which passed through the House on Wednesday.

The amendment would prevent the use of city funds to enforce virtually all local gun laws, meaning police and city officials could enforce only federal firearms laws. The city’s gun-control laws are among the tightest in the nation, restricting the open or concealed carrying of guns outside the home, banning assault-type rifles and high-capacity magazines, and requiring gun owners to register their weapons with D.C. police.

Those laws have previously been challenged by other bills and amendments, but Del. Eleanor Holmes Norton (D-D.C.) said the fact that Massie’s measure was able to pass the House presented a “clear and present danger” to District residents and visitors.

D.C. Mayor Vincent C. Gray (D) credited the District’s gun laws with helping to drive down violent crime, while Alfred Durham, an assistant D.C. police chief, said the amendment would make it harder for officers to protect the city.

Del. Eleanor Holmes Norton is seen in this 2012 file photo. (Marvin Joseph/The Washington Post)

Gray cited the Navy Yard shooting last September, in which the mentally ill perpetrator purchased his gun outside of the city, as evidence that the District’s gun laws were beneficial.

“That gun was not purchased in the District of Columbia,” Gray said. “That gun was not gotten from the District of Columbia. It came from a neighboring state, Virginia, whose gun laws are far more permissive than the District of Columbia and doesn’t have the level of background checks that we have.”

In a meeting with reporters shortly after the news conference, Massie said the Navy Yard shooting in fact demonstrated that D.C.’s gun control did not work and said “all their laws do right now is to keep honest citizens from having firearms and bearing firearms.”

As the fate of the amendment now passes into the Senate, Norton said she was hopeful that Democrats in the upper house would be able to strike Massie’s amendment during budget negotiations expected later this year.

Norton also said an appropriations bill was an “inappropriate vehicle” to try to overturn D.C.’s gun laws. The effect of Massie’s amendment, she said, is legally ambiguous and would invite “complicated litigation that could go on for years” should it become law.

“You want to overturn our laws, there’s only one way to do it in the Congress of the United States,” Norton said. “You got to introduce a bill, take that bill through the processes and have enough people agree with you to get it done.”

D.C. Council Chairman Phil Mendelson (D), who wrote many of the gun laws in question, also criticized Massie’s approach in a Wednesday release, calling his amendment “poorly drafted” and saying it could serve in some cases to make city gun laws more strict, not less so.

Massie acknowledged the inherent risk of amending an appropriations bill.

“I’m fairly confident that it will get killed by Harry Reid,” he said, referring to the Senate majority leader. “This was a rider on an appropriations bill and he has refused to pass any appropriations bill. I think he wants to have a giant omnibus at the end of the year.”

Regardless of its fate, Massie said, the amendment represented a valuable opportunity to get a gun-rights vote on the floor.

“The primary reason is to restore gun rights anywhere that I can,” he said.

Mike DeBonis contributed to this report.