(CNN) -- Donald Sterling is digging into his wallet to dig into the NBA and its owners.
In his latest salvo against the league that's moved to oust him over racist remarks, the embattled Los Angeles Clippers co-owner has hired "multiple private investigation firms" to look into alleged discriminatory conduct by fellow team owners and the NBA itself, said a person familiar with Sterling's legal strategy.
He will give each firm a budget of $50,000 and 30 days to finish an investigation, according to this source, who is not authorized to speak publicly and spoke to CNN on condition of anonymity.
The billionaire real estate mogul bought the Clippers in 1981 for about $12 million; his estranged wife, Shelly, recently reached an agreement with former Microsoft CEO Steve Ballmer to sell the franchise for $2 billion.
After initially signaling his openness to this deal, Sterling has backed off. Not only won't he sell the franchise -- as league leaders have insisted should happen -- but Sterling insists he won't pay a $2.5 million fine or accept a lifetime ban ordered by NBA Commissioner Adam Silver.
Sterling's camp recently filed a lawsuit against the NBA and its efforts to force a sale.
Asked whether the latest development -- hiring private eyes to look into the league's business and its 29 other owners -- means that Sterling has decided to take the proverbial gloves off to fight the NBA, the source familiar with his legal strategy said that assessment was not fair.
"I think the NBA took the gloves off," said the source, citing the league's actions and its siding in court with Shelly Sterling in her own efforts to finish off the Clippers' sale.
A source with knowledge of the NBA's position said Friday that the decision to hire private investigators "is not uncommon practice by lawyers to drum up allegations and scare tactics to attempt to obfuscate the real issue."
In this case, according to this source, the apparent aim is to cover up "the conduct of Mr. Sterling that led to his deserved ban and $2.5 million fine."
"This is not just obfuscation," the source added, "but a strategy of intimidation that will not work and only further demonstrate that Mr. Sterling is unfit to own a team."
Private eyes will probe bias cases, pay for execs
The source said that the private investigators will look into discrimination cases filed by African-Americans and women targeting the NBA.
Sterling's camp knows of at least 12 such cases of alleged discrimination dating back to 2008, about half of which involve pregnant women who filed complaints against the league office, said the source.
The investigators will also try to dig up instances where league owners made questionable remarks, including anything that would be considered sexist or racist, a source told the Associated Press. The AP described its source as a person familiar with Sterling's legal strategy, though it wasn't immediately clear whether this was the same person who talked to CNN.
Sterling came under fire in April, when TMZ posted audio of him talking to his companion V. Stiviano. The release spurred an uproar among league officials, fans and players, who reportedly threatened to boycott playing in the NBA playoffs if Sterling still was in control of the Clippers.
That's when Adam Silver stepped in, swiftly banishing Sterling from any team or league activities and promising to work to oust him as an owner. The Clippers co-owner defended his actions -- including a CNN interview that drew more harsh criticism for remarks about basketball legend Magic Johnson -- and went back-and-forth about what to do, before apparently settling on an all-out fight with the league.
Sterling voiced particular dismay about the NBA commissioner, who took over that job earlier in 2014 after years in the league office. To that end, the investigators he's hired will look into compensation paid to top NBA executives, past and present, according to CNN's source familiar with Sterling's legal strategy.
As to investigating fellow NBA owners, this source said Sterling was reluctant to do so, but felt he needed to at this time.
Dispute over Sterling's mental state, family trust
While a large-scale investigation certainly marks an escalation, it can't come as a total surprise.
Earlier this week, the 80-year-old Sterling defiantly called the NBA "a band of hypocrites and bullies" that needs to examine its own "discriminatory practices" rather than try to take away his personal property. This happened days after he sued the NBA for more than $1 billion over its decision to ban him for life and force him to sell the franchise.
"We have to fight for the rights of all Americans. We have to fight these despicable monsters," Sterling wrote in a statement, provided to CNN by Bobby Samini, one of his lawyers.
Talking to ABC about the Sterling accusation at the halftime of an NBA finals game between the San Antonio Spurs and the Miami Heat, Silver said he had "no idea what he's talking about."
"This is about Donald Sterling and his conduct," the commissioner said. "And if he wants to litigate, he'll litigate."
The NBA isn't alone in its fight.
It's joined by Shelly Sterling, who has asked a Los Angeles probate court to uphold her negotiated sale of the team despite her husband's objections.
The probate court will hold a four-day hearing next month that will focus on whether she has the power to sell the team if her co-owner is incapacitated. The AP source said the probate court decision prompted Sterling to hire the investigators.
"It's unfortunate. Mrs. Sterling regrets having to go to court and publicly air this problem," said her attorney, Pierce O'Donnell. "But Mr. Sterling's conduct in reneging on the sale requires her to do so."
Though the Clippers are owned by a family trust, Shelly Sterling's attorney has said three physicians certified that Donald Sterling lacks the mental capacity to function as a trustee.
"The trust agreement provides that if two qualified physicians certify that he's mentally incapacitated, he's removed," O'Donnell said.
Though she said three doctors have reviewed evidence and concluded that Donald Sterling is mentally incapacitated, his lawyer has said he is far from incapacitated.
CNN's Jill Martin contributed to this report.