People on the government’s terrorist watch list tried to buy guns nearly 1,000 times in the last five years, and federal authorities cleared the purchases 9 times out of 10 because they had no legal way to stop them, according to a new government report.
In one case, a person on the list was able to buy more than 50 pounds of explosives.
The new statistics, compiled in a report from the Government Accountability Office that is scheduled for public release next week, draw attention to an odd divergence in federal law: people placed on the government’s terrorist watch list can be stopped from getting on a plane or getting a visa, but they cannot be stopped from buying a gun.
Gun purchases must be approved unless federal officials can find some other disqualification of the would-be buyer, like being a felon, an illegal immigrant or a drug addict.
“This is a glaring omission, and it’s a security issue,” Senator Frank R. Lautenberg, the New Jersey Democrat who requested the study, said in an interview.
Mr. Lautenberg plans to introduce legislation on Monday that would give the attorney general the discretion to block gun sales to people on terror watch lists.
The government’s consolidated watch list, used to identify people suspected of links to terrorists, has grown to more than one million names since the attacks of Sept. 11, 2001. It also has drawn widespread criticism over the prevalence of mistaken identities and unclear links to terrorism.
A report in May from the Justice Department inspector general found that the list kept by the Federal Bureau of Investigation carried the names of 24,000 people included on the basis of outdated or sometimes irrelevant information.
Gun rights advocates said showing up on a terrorist watch list should not be grounds for being denied a gun.
“We’re concerned about the quality and the integrity of the list,” said Andrew Arulanandam, a spokesman for the National Rifle Association. “There have been numerous studies and reports questioning the integrity, and we believe law-abiding people who are on the list by error should not be arbitrarily denied their civil rights” under the Second Amendment.
Mr. Lautenberg introduced a similar gun-control measure in 2007, but it stalled after opposition from the N.R.A. The senator attributed the outcome to “knuckling under to the gun lobby.”
Mr. Arulanandam said the gun lobby would have to examine the details of the newest proposal before taking a position. But he added: “Senator Lautenberg has always been on the wrong side of the Second Amendment. His approach is not in the interests of public safety.”
The G.A.O. study found an increase in the last few years in the number of gun purchase requests and approvals for people on the terrorist watch list.
From February 2004 through February 2009, the report found, there were 963 requests for gun purchases through the federal system by people on the list. Of that group, 865 purchases — or 90 percent — were approved after a three-day review by the F.B.I. failed to turn up any other disqualifying factors.
A narrower study by the G.A.O. in 2005 first drew public attention to the issue. The Justice Department took some limited steps to address the issue, centralizing the review of gun purchases by those on watch lists to ensure that all possible disqualifiers were being considered.
Nonetheless, the rate of approval for requests to buy a gun went up from 80 percent in 2005 to the new study’s 90 percent. Officials were searching for explanations for the increase, which might reflect the overall growth in both the number of people on the watch list and of gun purchases.
The names of the people on the watch list are secret, and Mr. Lautenberg said he was frustrated by the F.B.I.’s refusal to disclose to investigators details and specific cases of gun purchases beyond the aggregate data.
The senator said that getting a better understanding of who is being allowed to buy guns and how people are connected to terrorism would help assess the need for legislative remedies.
The G.A.O. reported that the Justice Department in the Obama administration, however, was “noncommital” about whether it would develop guidelines if Congress moved to give the attorney general discretion to block such gun sales.