WASHINGTON — Former Comptroller of the Currency John Dugan will rejoin the law firm Covington & Burling.

The firm approved the appointment of Dugan on Monday to chair the firm's financial institutions group and to advise clients on regulatory requirements, including implementation of the Dodd-Frank Act, institution mergers, enforcement orders, international financial regulation and legislative and government issues. He will start at the firm in January after the holidays.

In an interview, Dugan said his experience as comptroller while Dodd-Frank was being debated will be valuable for clients.

"I think it's the kind of thing I know a lot about why the laws are put together, the way they were put together and there's awful lot of implantation that's going to go on," Dugan said. "I think I have a pretty good sense of why the law as enacted, the ways it was and the way regulators think about these rules."

Dugan was comptroller of the currency from 2005 to August 2010, a period of time that included the financial crisis, the creation of the Troubled Asset Relief Program, and the debate, passage and enactment of Dodd-Frank. He also served on the Federal Deposit Insurance Board.

Before the OCC, Dugan served as Treasury assistant secretary for domestic finance from 1989 to 1993. From 1985 and 1989, he was counsel and minority general counsel for the Senate Banking Committee. He first worked at Covington in 1993 and previously chaired the firm's financial institutions group.

Going forward, Dugan sees numerous challenges for the industry, including implementing Dodd-Frank and new, higher capital rules.

"Complying with Dodd-Frank, I think there is going to be a tremendous amount of uncertainty," Dugan said. "That's number one. No. 2 the government has proposed minimum rules on capital and liquidity standards. Those are difficult to do over time."

Further, he sees more opportunities for mergers and acquisitions.

"I think it's very possible there will be a great deal of mergers and acquisition activity as banks get healthier and face new compliance burdens," he said "I think there will be a new wave of that."