Nearly 900 people on the FBI’s terror watch list applied for and received a certificate to buy a gun in the United States between 2004 and 2009, according to a Government Accountability Office report released today.

In all, some 90 percent of the people on the watch list who applied passed the required background check, said the report, which was requested by Sen. Frank Lautenberg (D) of New Jersey.

Gun-control activists say the report demonstrates potentially lethal flaws in gun laws. But gun-rights advocates counter that the terror list is perhaps a greater menace in itself. They see it as ripe for manipulation – allowing the government to tar people as terrorists when it is politically expedient to do so.

The FBI can halt the purchase of a gun by someone with a criminal conviction, so the 900 people in the GAO report "are people who have no criminal conviction, but they're on this mystery list," says Gary Kleck, author of "Stopping Power: Why 70 million Americans own guns."

The GAO document is a follow-up to a 2005 report, which said the FBI cleared gun purchases for 80 percent of terror watch subjects who applied. The current report shows that the percentage has gone up: of 963 background checks, 865 were given the go-ahead – 90 percent.

There's currently no basis to automatically prevent a person from buying a gun simply because they appear on the terrorist watch list, wrote Ellen Larence, the GAO's director of homeland security and justice issues. There must be additional disqualifying factors, such as a felony conviction or illegal immigration status.

Senator Lautenberg calls this "the terror gap," and he wants to fix it with new legislation. His proposed law would give the US attorney general broad discretion to stop a purchase, but would also give affected gun-buyers a chance to appeal the decision. A similar bill failed in Congress last year.

To gun-rights advocates, Lautenberg is essentially trying to undermine the constitutional concept of due process in order to disarm law-abiding Americans.

"This report and the legislation originate from the idea that we can deprive people of basic constitutional protections based on allegations," says Larry Pratt, executive director of Gun Owners of America.

Gun owners have long said that gun restrictions impinge on due process. But the issue has taken on added significance in the current political climate, in which the Obama administration – through the Department of Homeland Security – has expressed concerns about the growth of right-wing extremism. A spate of politically-motivated killings in recent months involving white supremacists and American-born jihadists has only added to this concern.

Now, the report's conclusions will further play on fears in some quarters that the US government wants to clamp down on gun-owning Americans simply for having conservative views.

When you conflate serious terrorist threats with "a right-wing extremist being anyone not driving a Prius with an Obama sticker, then I start having a little bit of a problem," says Jeff Knox, director of the Firearms Coalition in Manassas, Va.

Civil libertarians, too, have concerns about the list. "There's no way to find out if you're on the list or not, and no way to assure that you can see the evidence that got you on the list or got you off," says Chris Calabrese, counsel for the ACLU's Technology and Liberty Project in New York.

"There's no reason why it couldn't become a political list," he says.