Although Quinn Emanuel removed Becker from the case after the bank's objection, Bank of America's lawyers argued that Becker's involvement broke ethical rules by placing Becker in a position to use his former clients' confidential information. But the judge disagreed.

Although Becker performed 5.8 hours of work for AIG on the case after his move, Quinn Emanuel promptly separated him from the case within 24 hours of discovering the conflict, the judge found.

“Screens erected immediately upon discovery of the conflict weigh against disqualification,” Jones wrote. Becker's minimal work on the case and his physical distance from it in firm's London office made any disclosure of confidential client information unlikely, she added. The size of Quinn Emanuel, with more than 500 attorneys, reduced that risk further, she wrote.

“There is no meaningful showing that the trial process here will be tainted,” Jones ruled. Given AIG's “significant” relationship with Quinn Emanuel and the cost of finding new counsel, she refused to disqualify the firm.

Marc Dworsky, a lawyer for Bank of America at Munger, Tolles & Olson, did not immediately respond to a request for comment.

Quinn Emanuel's other cases include most of the 18 Federal Housing Finance Agency lawsuits against Bank of America, other banks and at least 131 individuals to recover losses on $200 billion of soured mortgage debt held by Fannie Mae and Freddie Mac.

The case is American International Group Inc v. Bank of America Corp et al, U.S. District Court, Southern District of New York, No. 11-06212.