By LARRY NEUMEISTER, Associated Press

NEW YORK -A lawyer who has sued Don King several times - and cost him millions of dollars - has gone to work for the boxing promoter.

The lawyer, Judd Burstein, once vilified King as a cancer on the sport but has now come to praise him as "extremely honorable."

As for King, he's also come around: He once called Burstein an "insidious insect" but now describes him as tenacious, hardworking and energetic.

"I respect his talent," King said. "He's on our side now."

Burstein had a string of successes against King in seven cases he brought between 1997 and 2004, including a $7.5 million settlement from him on behalf of boxer Terry Norris.

The 52-year-old Burstein said he called reporters afterward and told them: "Don King was a cancer on the sport and the settlement was a dose of chemotherapy."

King once sued the lawyer for defamation in England after Burstein claimed King was anti-Semitic. The case was settled.

"He and I had always had this weird love-hate relationship," Burstein said. "He had a lot of respect for me because I won cases against him."

Burstein said his change of heart came after he represented IBF boxing champion Chris Byrd in a lawsuit against King in 2004. Byrd said King stiffed him on a contract that guaranteed Byrd $2.5 million for each title defense.

Burstein said Byrd was supposed to pay him a flat fee of $250,000 and 25 percent of any amount over $1 million. Within a day, Burstein said King agreed to pay the $2.5 million but Byrd refused to pay some of Burstein's fee on the grounds that it had been earned too quickly.

Last month, Burstein sued Byrd on King's behalf, claiming the 35-year-old boxer owes King at least $4 million for disrupting his plan to unify four major heavyweight titles when he refused to participate in a tournament King sought to promote.

On Friday, Byrd's new lawyer, Patrick English, wrote to a federal judge in Newark, N.J., arguing that King's company, Don King Productions Inc., had used "strong-arm" tactics against his client with the direct participation of Burstein.

He said Burstein had promised when he joined King not to work directly on litigation involving Byrd but instead worked to sabotage Byrd's case.

"Put bluntly, Chris Byrd was sandbagged by the Burstein firm," he wrote.

Burstein said his work on the case was within legal bounds. "I don't think, under the law, I'm disqualified," he said.

Ronald Minkoff, a lawyer, is president of the Association of Professional Responsibility Lawyers, a nationwide organization of about 300 lawyers who specialize in the legal profession. He said it was well established that a lawyer cannot sue a former client on the same or a substantially same matter.

"Is it common that people turn around and sue their former clients? No. That's why we have this rule. People know the rule and follow this rule," Minkoff said.

Bruce Green, a professor specializing in legal ethics at Fordham Law School, said it was not common for attorneys to sue former clients but that it occurs often enough that states have rules to protect adversaries in such situations.

Burstein said King's cases made up about 10 percent of his firm's business last year. He added that he has turned down a large amount of boxing-related business because it would require him to take positions contrary to King.

"He's taken me out of the mix," he said. "Having me has made people less likely to litigate against him."

Burstein was philosophical about what he has learned about the boxing profession.

"This is a business where nobody's going to win awards for conduct," he said. "It is a world where loyalty is almost a four-letter word."

He added, "It's a sport I love, but it's a cesspool."