What that means is that those fugitives who were previously prohibited under federal law from purchasing firearms can now buy them, unless barred for other reasons.
Since the National Instant Criminal Background Check System (NICS) was created in 1998, the background check system has prevented 1.5 million people from buying guns, including 180,000 denials to people who were fugitives from justice, according to government statistics.
It is unclear how many people may have bought guns since February who previously would have been prohibited from doing so.
Attorney General Jeff Sessions sent a memo Wednesday to the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives instructing them to take several steps to improve NICS.
The system, he said, is "critical for us to be able to keep guns out of the hands of those . . . prohibited from owning them."
The criminal background check system has come under scrutiny in recent weeks after the Air Force said it failed to follow policies for alerting the FBI about the domestic violence conviction of Devin P. Kelley, who killed more than two dozen churchgoers in Sutherland Springs, Tex., this month. Because his conviction was not entered into NICS, Kelley was allowed to buy firearms.
Two years ago, Dylann Roof, who killed nine people at a historic black church in Charleston, S.C., was able to buy his gun after errors by the FBI and local law enforcement led to his name not being entered into criminal record databases when he was arrested and had admitted to drug possession.
The interpretation of who is a "fugitive from justice," a category that disqualifies people from buying a gun, has long been a matter of debate in law enforcement circles — a dispute that ultimately led to the February purging of the database.
"Any one of these potentially dangerous fugitives can currently walk into a licensed gun dealer, pass a criminal background check, and walk out with a gun," Robyn Thomas, executive director of the Giffords Law Center to Prevent Gun Violence, wrote in a letter to FBI Director Christopher A. Wray on Wednesday. The Giffords organization, founded by former Arizona congresswoman Gabrielle Giffords, called on the FBI and ATF to "correct this self-inflicted loophole" and recover all guns illegally purchased this year because of the purge of names from the database.
For more than 15 years, the FBI and ATF disagreed about who exactly was a fugitive from justice.
The FBI, which runs the criminal background check database, had a broad definition and said that anyone with an outstanding arrest warrant was prohibited from buying a gun. But ATF argued that, under the law, a person is considered a fugitive from justice only if they have an outstanding warrant and have also traveled to another state.
In a 2016 report, Inspector General Michael E. Horowitz urged the Justice Department to address the disagreement "as soon as possible." Late last year, before President Trump took office, the Justice Department Office of Legal Counsel sided with ATF and narrowed the definition of fugitives, according to law enforcement officials. The office said that gun purchases could be denied only to fugitives who cross state lines.
After Trump was inaugurated, the Justice Department further narrowed the definition to those who have fled across state lines to avoid prosecution for a crime or to avoid giving testimony in a criminal proceeding.
On Feb. 15, the FBI directed its employees in the Criminal Justice Information Services Division to remove all entries of fugitives from justice from the background check database and said that "entries will not be permitted" under that category until further notice. Before the FBI memo, there were about 500,000 people identified as fugitives from justice in the database — and all of those names were removed.
Now there are 788.
"Even if the FBI's revised definition of fugitive from justice is assumed to be legally correct, purging the NICS database of every single individual previously identified as a fugitive from justice was an unjustifiable, alarmingly overbroad, and dangerous decision," the Giffords group's Thomas and Robin F. Thurston of the Democracy Forward Foundation wrote in the letter to the FBI.
Federal law enforcement officials say that about 430,000 names of wanted people removed from the database were from Massachusetts.
Commissioner James Slater of the Massachusetts Department of Criminal Justice Information Services said that the reason that his state had so many fugitives in the FBI database is that state policy required sending the bureau the names of all people with an outstanding warrant, whether it was for misdemeanors or felonies.
Because Massachusetts state law prevents fugitives from buying guns, those individuals have now been added back to the federal database under the "state prohibitor" category and will be prevented from purchasing a firearm, he said.
Of the 70,000 others whose names have been purged, the FBI is working with the states to identify which people might have crossed state lines and could be put back into the federal database for that or other reasons.
"The Justice Department is committed to working with law enforcement partners across the country to help ensure that all those who can legally be determined to be prohibited from receiving or possessing a firearm be included in federal criminal databases," said a Justice Department official who would discuss the matter only on the condition of anonymity.
Sessions in his memo directed the FBI and ATF to work with the Defense Department and other government agencies to improve reporting and identify any other measures that could be taken to prevent guns getting into the wrong hands.
David Chipman, a former ATF official who now works as a senior adviser to the Giffords group, said that, given the confusion over the definition of a fugitive, Congress should pass a new law that makes clear whether people with outstanding arrest warrants can buy a gun.
"I would imagine 99 percent of Americans don't want people who have a warrant out on them to be able to buy a gun," Chipman said. "I can't believe there is a constituency for wanted people. Wanted people are particularly dangerous. They've already proven that they'll break the law."
This story has been updated to clarify that the database was purged by the FBI after the Justice Department changed its legal interpretation of "fugitive from justice."