The FBI raided the offices of President Donald Trump's personal attorney, Michael Cohen, on Monday, according to a statement by Cohen's own attorney, McDermott Will & Emery partner Stephen Ryan.

According to the statement posted on the firm's website, the FBI seized privileged communications between Cohen and “his clients” on behalf of the U.S. Attorney's Office for the Southern District of New York, Ryan said. The move was taken, in part, through a referral by the Office of Special Counsel, Robert Mueller, according to Ryan.

According to Ryan, the move by the office of U.S. Attorney Geoffrey Berman was “completely inappropriate and unnecessary.”

“It resulted in the unnecessary seizure of protected attorney-client communications between a lawyer and his clients,” Ryan said. “These government tactics are also wrong because Mr. Cohen has cooperated completely with all government entities, including providing thousands of non-privileged documents to the Congress and sitting for depositions under oath.”

Cohen has long served as Trump's personal lawyer ahead of his election as president in 2016. Most recently, Cohen has found himself at the center of controversy over a $130,000 payment he said he made on his own to adult film actress Stephanie Clifford, who goes by Stormy Daniels, just before the election.

A spokesman for the Manhattan U.S. Attorney's Office declined to comment.

An attempt to reach Cohen by phone and email was unsuccessful. In a statement, Squire Patton Boggs said Monday that it had ended its formal working relationship with Cohen following the raid.

Berman was appointed by U.S. Attorney General Jeff Sessions in January, pending a nomination by Trump for confirmation by the U.S. Senate. That nomination has yet to be made. U.S. Senator Kirsten Gillibrand of New York has vowed to block Berman's nomination over reports Trump personally interviewed Berman, then a shareholder at Greenberg Traurig, ahead of his appointment.

The privileged communications seized by prosecutors will require a special process for federal agents and prosecutors to be able to use them, according to former prosecutors with experience handling communications usually protected by attorney-client privilege.

A firewall is erected between the “dirty” side of the investigation—agents and prosecutors who conduct a filter review of the material that may include information the government should not be privy to. Any communications authorities want to be able to use requires the petitioning of a court for a crime fraud exception. The communications would have to show the attorney was perpetuating or facilitating a criminal act.

Once the judge involved in the case grants the petition by the “dirty” side of the investigation, the relevant information that's been cleared is handed off to the “clean” side who proceed with the investigation.

This would not be the first time federal investigators sought a crime fraud exception to the attorney-client privilege. Recently, U.S. District Chief Judge Beryl Howell of the District of Columbia granted the government's request to compel an attorney connected to Trump's former campaign manager Paul Manafort to testify before a grand jury in that prosecution.