After the Senate’s failure to adopt gun control legislation , Republican Sen. Susan Collins and a bipartisan coalition Tuesday announced a compromise proposal to bar some terror suspects from buying guns.

But the White House and Justice Department are holding off on backing the measure until they study its provisions. And one leading Democrat, New York Sen. Charles E. Schumer, said there are several key flaws that would need to be fixed before the proposal moves forward.

And the NRA said late Tuesday afternoon that it would oppose the measure, which could keep more Republicans from signing onto the bill.

“Senator Collins and others are focusing their efforts on unconstitutional proposals that would not have prevented the Orlando terrorist attack,” NRA executive director Chris W. Cox said in a statement

Collins, R-Maine, has been working with colleagues on both sides of the aisle on the emerging proposal to bar firearms from being sold to individuals on what are known as the “Selectee” and “No Fly” lists, rather than the considerably larger “Consolidated Terror Watchlist.”