Donald Sterling filing $1B lawsuit

— -- Donald Sterling isn't done fighting yet. 

The banned Los Angeles Clippers owner is filing a $1 billion lawsuit against the NBA, his lawyer confirmed to ESPN.com's Ramona Shelburne on Friday.

The news came just hours before the NBA announced that it had approved Shelly Sterling and the Sterling family trust's deal for the Clippers with former Microsoft executive Steve Ballmer, who bid $2 billion for the team. That deal now must be approved by the NBA's Board of Governors.

"The [termination] charges in the lawsuit are an invasion of his constitutional rights, violation of antitrust laws, breach of fiduciary duty and breach of contract," attorney Max Blecher said.

Blecher said the lawsuit was being filed Friday afternoon and "has nothing to do with the sale." He said Sterling is still weighing legal action against his wife, saying: "He's looking at it. That's a different kettle of fish. We just got the paperwork on that yesterday. There's been no decision made on that yet."

Donald Sterling repeatedly has vowed to fight the NBA's attempts to force him to sell the team. That fight was temporarily derailed this week after sources say he was found by experts to be mentally incapacitated, paving the way for Shelly Sterling to become the sole trustee of the family trust and empowering her to work on an agreement to sell the team to Ballmer.

Earlier in May, two neurologists conducted a number of brain tests on Sterling, 80, at the urging of his family, a source said. Their diagnosis was that he was suffering from Alzheimer's disease, and likely had been for "three to five years."

Sterling's side, as well as his wife's attorneys, had known of the tests' results for some time, the source said. The family trust has rules and guidelines regarding mental incapacitation, which it defined as an inability to conduct normal and regular business affairs. 

Earlier Friday, Blecher confirmed in an email to ESPN that evaluations were performed on his client but said the results of the neurologists' examinations were "grossly exaggerated" and that "Mr. Sterling is far from mentally incompetent." In similar comments to CNN, Blecher said it was determined that Sterling had "modest mental impairment" or "a slowing down." 

Shelly Sterling and her advisers initially had hoped to sell the team without using her husband's incapacitation as a reason, according to sources. However, when Donald Sterling said in his response to the NBA that he intended to fight the sale of the team, they changed course and signed an agreement to sell, citing the terms of the trust.

The rules of the trust did not require a court hearing first to declare that Donald Sterling is mentally incapacitated. That allowed Shelly Sterling to negotiate directly with Ballmer and the league to sell the team.

ESPN.com's Ramona Shelburne and Darren Rovell contributed to this report.