An F.B.I. analyst improperly used a high-profile warrantless surveillance program to conduct overly broad searches about two lawmakers, including a U.S. senator, last June, a newly declassified court ruling released on Friday shows, even as the bureau has overall improved compliance with limits on the program.

In the June 2022 episode, the analyst had a legitimate reason for searching for information about the legislators, who also included a state lawmaker, in a repository of intercepts, the ruling said, because evidence suggested that they were targets of a foreign intelligence service. But the queries were too wide-ranging, using only their last names without limiting terms to screen out irrelevant material, it said.

The episode is likely to fuel criticism of the program, which is set to expire at the end of the year, as Congress debates whether or how to enact legislation to extend it. A series of earlier disclosures about recent violations of querying standards by the F.B.I. — many of which took place before a series of internal changes in 2021 and 2022 — has given fodder to its skeptics.

Known as Section 702, the law traces back to 2008 when Congress legalized a version of a warrantless surveillance program secretly created after the attacks of Sept. 11, 2001. It allows the government to collect, from American companies like Google and without a warrant, the communications of targeted foreigners abroad in order to gather intelligence about foreign governments, terrorists and proliferators of weapons of mass destruction.

Because that can sweep in targets’ communications with or about Americans, privacy-minded lawmakers have long sought to impose greater limits on the program. But in previous cycles when Section 702 was about to lapse, they have been outvoted by hawks and centrists of both parties. This time, however, its liberal critics are joined by a faction of Republicans who have aligned themselves with former President Donald J. Trump’s hostility to the “deep state” and see the issue as a chance to impose pain on the F.B.I.

The newly declassified opinion, issued in April by Rudolph Contreras, the presiding judge of the Foreign Intelligence Surveillance Court, also showed that the National Security Agency this year gained broadened authority to run queries of Section 702 information using the identifiers of foreigners who are planning to visit the United States.

But the main political impact of the ruling is likely to be its discussion of the F.B.I., which adds to a series of revelations by the government over the past year in which it has acknowledged significant violations of the Section 702 querying standard by the bureau. (Under the standard, there must be specific reason to believe that the search will return foreign intelligence information or evidence of a crime.)

In May, a declassified ruling from April 2022 by Judge Contreras disclosed that officials had improperly queried for information about hundreds of Americans who had come under scrutiny in connection with the racial justice protests after the 2020 police killing of George Floyd and the Jan. 6, 2021, attack on the Capitol.

The newly released opinion cited another episode involving the Jan. 6 investigation: In March 2022, an F.B.I. agent ran a query on an American that did not meet the standard. The agent also looked at information that came up without obtaining a court order, which is required to view any results from queries about Americans for purely criminal investigations. The judge wrote that the Justice Department informed him about that in September.

The opinion did not make public the identities of the lawmakers who had been subject to overly broad searches, but the member of Congress was notified, officials told reporters in a background briefing on Friday.

The opinion also disclosed an October 2022 incident in which an F.B.I. official ran a query using the Social Security number of a state judge who had complained to the F.B.I. about civil rights violations supposedly committed by a municipal chief of police.

The opinion provided no further explanation for that incident. An official familiar with the matter said it had led to accountability measures but declined to provide further details.

Still, Judge Contreras offered cautious praise for steps the F.B.I. had taken in 2021 and 2022 to cut down on such violations. Those include changing its computer system so that when agents conduct general searches of F.B.I. databases, the Section 702 database is excluded by default, and requiring officials to specify their reasons for searching for an American’s identifier.

Since those broader changes took effect, F.B.I. queries for information about Americans in the Section 702 repository — and problematic searches — have dropped. Judge Contreras wrote that the number of queries about Americans is now about 160,000 to 200,000 a year, and a recent audit suggested about 1.7 percent fail to comply with standards.

“Despite the reported errors, there is reason to believe that the F.B.I. has been doing a better job in applying the querying standard,” he wrote. “In some cases, F.B.I. personnel apparently misapplied the querying standard to a group of similarly situated persons, but those violations do not approach the scale of a number of prior ones.”

The improving numbers were “encouraging,” the judge said, cautioning that assessment was incomplete. The Justice Department audits samples, not all queries, meaning that it remained “possible that serious violations of the querying standard have so far gone undetected,” he wrote. “On balance, however, F.B.I. application of the querying standard appears to have improved.”

As a matter of political reality, Mr. Trump’s hard-right allies in the House are unlikely to vote to extend Section 702. So the future of the program may boil down to what new limits on the program they could see as sufficient to allow Speaker Kevin McCarthy to bring a reauthorization bill to the floor — even if they will still oppose it. Because of the concessions Mr. McCarthy had to make to secure the speakership, that hard-right faction has the power to topple him, and its members are already angry that he permitted a vote to suspend the debt ceiling.

Civil liberty and privacy activists have long pushed to require the government, or at least the F.B.I., to obtain a court warrant before using Americans’ identifiers to search the repository of intercepted communications. They see the present odd-bedfellows alliance with the hard-right Republicans as a unique opportunity to achieve that reform.

Elizabeth Goitein, co-director of the Brennan Center for Justice’s Liberty and National Security Program at New York University Law School, said that a 1.7 percent rate of botched queries still works out to thousands a year. But, she added, the query standard itself was too permissive to protect Americans’ privacy.

“Even if the F.B.I. had achieved perfect compliance with its own rules, that wouldn’t obviate the need for a warrant,” she said.

National security officials say a warrant requirement would cripple the F.B.I.’s ability to use the program effectively for its missions, including “defensive” queries using the identifiers of Americans targeted by foreign hackers and spies. They hoped that limits they have imposed since 2021 will persuade Congress that any further curbs should fall short of such a requirement.

In a letter to Congress on Friday, the F.B.I. director, Christopher Wray, suggested making the recent reforms law as part of reauthorizing Section 702, and listed ways the program has been useful against threats like Chinese and Iranian hackers and spies. He disclosed that “97 percent of the F.B.I.’s raw technical reporting on malicious cyberactors, and 92 percent of our reporting on emerging technologies, such as artificial intelligence, came from Section 702.”

The bureau, he added, welcomed discussion about further overhauls and how they could be enacted “without diminishing Section 702’s vital intelligence value.”

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