In a rare move, a secretive federal surveillance court this week found that the FBI misled judges about the rationale for wiretapping a former Trump campaign adviser and ordered the bureau to propose changes to ensure that it doesn’t happen again.

And as Congress tackles impeachment, the FBI’s apparent abuse of the FISA process is a key subplot in the wake of scathing findings released last week by the Justice Department inspector general about the FBI’s missteps during its investigation into the Trump campaign’s alleged ties to Russian officials. Sen. Lindsey Graham has said that in the New Year he plans to make reform of the Foreign Intelligence Surveillance Court process a top priority for the Senate Judiciary Committee, which he chairs.

Allowing government surveillance of private citizens has been an explosive topic ever since laws expanding the practice were passed after the 9/11 attacks.

But several former law enforcement officials say they also are troubled by other aggressive and unorthodox FBI tactics used to investigate Trump campaign operatives. Chief among them was a counterintelligence briefing the Office of the Director of National Intelligence provided to the Trump campaign, but which was also used to collect information for the FBI’s Russia probe.

Inspector General Michael Horowitz found that the supervising agent overseeing the FBI’s Russia investigation attended the counterintelligence briefing, and a week later the agent documented questions he asked then-candidate Trump and his top foreign policy adviser, Michael Flynn.

In essence, Horowitz said, the FBI used a briefing ostensibly focused on guarding against foreign interference as a “pretext” to gather evidence on Trump and Flynn and help further the Russia investigation. Hillary Clinton’s campaign also received a similar briefing but the FBI didn’t use it to collect information on her or her team.

“We concluded that the FBI’s use of this briefing for investigative reasons could potentially interfere with the expectation of trust and good faith among participants in strategic intelligence briefings, thereby frustrating their purpose,” Horowitz’s report said.

In condemning that FBI action last week, Graham referred to a defensive FBI briefing the full Senate was set to receive and wondered aloud if it would be used to gather intelligence on senators.

“I hope that doesn’t happen to us tomorrow — I’ll be really pissed if it does,” he said when questioning the IG during a Judiciary Committee hearing last week. “When we get defensively briefed tomorrow, would it be okay for FBI agents to open up 302s [FBI interview notes] on what we said?”

Horowitz responded that his team has “very significant concerns” about such a practice. He said FBI Director Christopher Wray has promised that it will not occur again.

Wray’s vow, however, doesn’t go far enough for some longtime law enforcement officials. These critics say Horowitz’s findings are just the beginning of the overhaul needed to restore public trust in the FBI. They also are looking to U.S. Attorney John Durham’s criminal inquiry into the FBI’s handling of the Russia investigation for more definitive answers along with punishment for the myriad mistakes, unorthodox tactics, and evidence of political bias against Trump.

George Terwilliger III, a partner at the law firm McGuireWoods, served in the Justice Department for 15 years, including as a deputy attorney general during the George H.W. Bush administration. In a Washington Post op-ed last week, Terwilliger argued that the FBI’s “unprecedented use of investigative authority” uncovered in Horowitz report deserves more scrutiny and shouldn’t be “taken as the final word on the FBI’s investigation.”

“It is absolutely critical to maintaining the integrity of the FBI and its work that these matters be thoroughly, objectively and timely investigated,” he wrote.

While Terwilliger focused his comments on the problems surrounding the FBI’s FISA application to wiretap Trump campaign adviser Carter Page, he too is troubled by the bureau’s decision to use an intelligence briefing of the Trump campaign as a way to gather evidence on the candidate and his top aides.

“If that briefing was a subterfuge for an investigation, that’s just wrong, and to me, if that were the case, it speaks to the gotcha mentality that’s out of place at the FBI,” he told RealClearPolitics.

“The general principle has to be that if you’re providing a briefing of that nature, it shouldn’t be undertaken in whole or part for investigative purposes. … It just destroys the credibility that’s necessary for those briefings to work.”

James Trusty, a veteran prosecutor who served as the chief of the Justice Department’s Organized Crime Section, called the FBI’s use of an intelligence briefing to gather evidence on individuals receiving the briefing the “ultimate backstab.”

“It’s the ultimate backstab to literally say we’re coming to warn you of something that we’re investigating because we’re looking out for you and to be actually using that as a camel’s nose under the tent,” he said in an interview.

“If you try to justify that approach by saying the agent was just there to listen, as opposed to engage in conversation, that’s garbage,” he added. The supervisory agent who participated in the briefing “knew Flynn would likely have something to say or he wouldn’t have gone to the briefing in the first place.”

Horowitz in his report noted that there were not FBI policies in place at the time detailing how briefings of politicians and candidates for federal office should be treated and whether it’s legal or appropriate to use them to try to gather evidence.

“We identified no Department or FBI policies or proceedings regarding the handling of presidential transition briefings, and no requirement that Department leadership be consulted before using a presidential transition briefing, or defensive briefing, for possible investigative purposes,” the report states.