WASHINGTON (AP) — An association of thousands of FBI agents and other groups are backing a lawsuit filed by three bureau employees who were fired last year for their roles in an investigation into President Donald Trump’s efforts to undo the results of the 2020 presidential election.

A legal brief by the FBI Agents Association is one of five filed by outside parties in the last week in support of the agents, who were terminated as part of a broader personnel purge by FBI Director Kash Patel that has targeted employees who investigated Trump or are perceived as being against the administration’s interest.

Taken together, the filings, including from former FBI and Justice Department alumni, underscore a concerted and bipartisan pushback to the waves of terminations that have roiled the FBI in the last year and a half as Patel has sought to remake the bureau in his own image.

The briefs argue that the firings were illegal because the agents were denied due process and punished for perceived political affiliation, and say the terminations contradict decades of expectations that the bureau’s “apolitical, professional career corps of agents” can work on sensitive cases without putting their careers at risk.

“The Bureau simply cannot function if individual Special Agents must choose whether to accept a lawful assignment that could later get them fired, or alternatively to reject it and become subject to firing for insubordination. FBI Special Agents have long understood that they are subject to assignment and reassignment at any time based on the needs of the Bureau,” the agents association, which serves nearly 12,000 members, wrote in its brief.

A brief filed by former senior Justice Department officials says the firings have undermined a “half-century of independence as a guiding principle.”

“Putting aside the resulting violation of Plaintiffs’ rights, the inevitable impact of this ‘purge’ will be to chill the independence of remaining and future career agents, attorneys, analysts, and other staff at the FBI, DOJ and other law enforcement agencies who must now act with the understanding that their investigative and law enforcement judgments can, for the first time in their careers, be assessed through a partisan political lens,” the brief states.

The three agents — Michelle Ball, Jamie Garman and Blaire Toleman — said in a federal lawsuit filed in March that they were fired in a “retribution campaign” targeting them for their work on the investigation into Trump. The agents performed “exemplary and unblemished” service in the FBI and expected to spend the remainder of their careers at the bureau but were abruptly fired without cause and without being given a chance to respond, the lawsuit says.

The investigation the agents worked on culminated in an indictment from special counsel Jack Smith that accused Trump of scheming to overturn the 2020 election he lost to Democrat Joe Biden.

Smith ultimately abandoned that case, along with a separate one accusing Trump of illegally retaining classified records at his Mar-a-Lago estate in Palm Beach, Florida, after Trump won back the White House in 2024, citing Justice Department legal opinions that prohibit the federal indictments of sitting presidents.

Patel and Pam Bondi, who was the attorney general at the time, have said the fired agents and prosecutors who worked on Smith’s team were responsible for weaponizing federal law enforcement, a claim that was also asserted in their termination letters but that the plaintiffs call defamatory and baseless.

The filings are known in the law as amici, or friend-of-the-court, briefs. They are sometimes submitted by outside parties in lawsuits to help stress particular arguments or inform a judge’s thinking.

Other groups who submitted briefs include a collection of First Amendment Scholars, a group called Lawyers for the Rule of Law, and Justice Connection, a network of department alumni that warned in its filing that a “politicized” FBI could turn against citizens because of their speech, association or perceived disloyalty.

“The Constitution,” the filing said, “is designed to prevent precisely this kind of abuse.”