Lanny Breuer, one of the longest-serving heads of the Justice Department’s criminal division, is returning to Covington & Burling, the law firm plans to announce today.

The firm’s partners voted Monday to approve Breuer’s return. He will step into the newly created position of vice chair, working with the firm’s senior leaders on long-term strategy and international growth, and will also practice in white collar defense and investigations.

Covington has represented corporations that were investigated by the criminal division during Breuer’s time as division chief. Breuer said he will not be representing any companies on any matters that went before the Justice Department during his tenure. Ethics rules bar him from appearing before the DOJ on a client’s behalf for two years. He can, however, counsel a client on a new matter before the department from behind the scenes.

“I’m sure that if we have a client that has a new matter and we’re able to get that work, I would get involved,” Breuer said in an interview.

Breuer is the latest high-profile hire that Covington, the District’s largest law firm with more than 500 attorneys locally, has snapped up amid Washington’s revolving door of high-ranking officials leaving government for the private sector. Veteran Calif. congressman Howard Berman and former Sen. Jon Kyl (R-Ariz.) both joined the firm’s lobbying practice this month. Covington is also the firm where Attorney General Eric Holder was a partner.

Breuer announced his resignation in late January, shortly after Frontline aired a piece sharply criticizing his division’s failure to bring criminal charges against Wall Street executives over securitizing bad mortgages that helped spur the financial meltdown in 2008.

The Frontline piece, Breuer said, had “zero to do with my decisions.”

“I always said I was going to leave, I thought, after the first term,” he said.

He said not a single U.S. Attorney’s office brought criminal charges against financial institutions over securitization.

“The fact that they weren’t brought by 94 different U.S. Attorneys’ offices and by the criminal division should suggest that a lot of the conduct people are upset with, which I understand are horrible and very upsetting, doesn’t make it criminal,” he said. “It’s as simple as that.”

As assistant attorney general, Breuer oversaw nearly 600 lawyers and steered the department in bringing some of the largest criminal cases in U.S. history, including the case against BP over the 2010 Deepwater Horizon disaster that killed 11 people. BP pleaded guilty to 14 criminal counts, including manslaughter, and agreed to pay a $4 billion settlement.

The criminal division also went after banks involved in manipulating the London interbank offered rate, or Libor — an effort that has produced more than $2 billion in penalties and fines from banks — and brought two of the largest Medicare fraud cases in history. Under his watch, the criminal division created the Human Rights and Special Prosecution Section, which prosecutes human rights violators for genocide, torture and war crimes.

Breuer’s time was also marked by criticism over federal agents’ botched efforts to track and halt the flow of U.S. guns to Mexican drug cartels by allowing some weapons to be transported illegally, an operation known as “Fast and Furious.” Two of the guns that flowed through turned up at a scene where a U.S. Border Patrol agent was shot and killed.

Sen.Chuck Grassley (R-Iowa) and Rep. Darrell Issa (R-Calif.) called for Breuer’s resignation over the matter, which was handled by the Bureau of Alcohol, Tobacco, Firearms and Explosives, a unit of the Justice Department.

The Justice Department’s inspector general issued a report last September that criticized several senior Justice officials for lax oversight in the gun operation, and recommended that the department review the actions of 14 officials including Breuer and consider whether it called for disciplinary action. The department found no wrongdoing on Breuer’s part.

Breuer previously worked at Covington from 1989 to 1997, before joining the White House as special counsel to President Bill Clinton; he defended Clinton during his 1998 impeachment trial. He returned to the firm in 1999 as co-chair of the white collar defense and investigations group until 2009, when he joined the Obama administration.

During his time at the firm, Breuer represented such corporate interests as ExxonMobil, the pharmaceutical lobby PhRMA, Cisco Systems and Freddie Mac in a 2008 congressional investigation of the financial crisis.