Voting rights advocates circulated a legal memo Thursday that calls a controversial gun amendment in the Senate-passed District of Columbia House Voting Rights Act outdated and unnecessary.

Sen. John Ensign (R-Nev.) offered the amendment in February, and Senators attached it with a vote of 62-36. The threat of a similar amendment has stalled the bill’s progress in the House, and House leaders have spent weeks trying to find a compromise.

But a memo by the law firm Patton Boggs, written for the advocacy group DC Vote, claims that several provisions in the amendment don’t address recent changes in the city’s gun laws.

D.C. officials revamped their strict laws after the Supreme Court issued an opinion last year calling them unconstitutional. Those changes, according to the memo, have put District guns laws in compliance with the Supreme Court decision, District of Columbia v. Heller.

Some Members, however, say the new laws are still too prohibitive. Ensign, in fact, claims his amendment restores Second Amendment rights to District residents.

But Ensign’s language “does not take into account the dramatic changes already made by the District to comply with the Supreme Court decision,— according to the memo. “The Ensign amendment includes provisions which are no longer viable and which negate policies that are currently employed by other states.—

Ensign’s office did not immediately return a request for comment.

Among other things, the amendment would repeal registration requirements for guns, prohibit the city from enacting firearm laws and allow residents to carry assault rifles like AK-47s and Uzis.

But under D.C. law, residents can only buy ammunition for guns they are registered to own, a requirement that would not be changed by the Ensign amendment. The result, the memo points out, would be to force owners to bring their guns with them when they wanted to buy ammunition, since that would be the only way to prove ownership.

It all adds up to language that is “duplicative, yet inconsistent,— according to Patton Boggs’ attorneys.

DC Vote sent out a press release with the memo attached Thursday afternoon, less than a day before D.C. Del. Eleanor Holmes Norton (D) will hold a hearing on how Ensign’s amendment will affect the security of the city.

She’s hoping a more thorough look at the effects of the legislation will convince more centrist and conservative Democrats to reject it and vote to consider an amendment-free D.C. voting rights act.