Hunter Biden’s legal team went on the offensive Wednesday, demanding state and federal investigations into the dissemination of material from his laptop, and threatening a defamation lawsuit against Fox News’ Tucker Carlson for allegedly failing to correct false statements.

The flurry of letters to the Delaware attorney general, the Department of Justice, the I.R.S. and attorneys for Fox News and Carlson represent an aggressive new strategy for the president’s son, who is facing long-running federal criminal investigations, as well as new probes promised by congressional Republicans, according to a source familiar with Biden’s approach.

“This marks a new approach by Hunter Biden and his team,” the source told CBS News. “He is not going to sit quietly by as questionable characters continue to violate his rights and media organizations peddling in lies try to defame him.” 

Attorneys for Hunter Biden called for Delaware Attorney General Kathy Jennings and U.S. Assistant Attorney General for National Security Matthew G. Olsen to launch investigations into the actions of former computer repair shop owner John Paul Mac Isaac, former Trump advisers Rudy Giuliani and Stephen Bannon, their attorney Robert Costello and others “for whom there is considerable reason to believe violated various Delaware laws in accessing, copying, manipulating, and/or disseminating Mr. Biden’s personal computer data.”

The Delaware Attorney General and Justice Department did not reply to requests for comment. CBS News has also reached out for comment to representatives for Mac Isaac, Giuliani and Bannon, as well as Fox News.

According to Mac Isaac, Hunter Biden dropped off the computer at a store in Delaware for repairs in April 2019 and never returned to pick it up. He has said he waited the 90 days required by his store’s customer service policy before considering the laptop abandoned. In court filings, Mac Isaac stated that he turned over the computer to the FBI but also provided a copy of its contents to Costello.

Purported copies of the laptop were widely circulated by Republican operatives to attack then-candidate Joe Biden before the 2020 presidential election, and the New York Post published a series of stories from the data.

“This failed dirty political trick directly resulted in the exposure, exploitation, and manipulation of Mr. Biden’s private and personal information,” Abbe Lowell, an attorney for Hunter Biden, wrote in his letters to Jennings and Olsen.

Costello, an attorney for Giuliani and Bannon, has previously defended their efforts to publicize the laptop, and said Giuliani offered to provide its hard drive to FBI agents “on several occasions,  but the agents steadfastly declined.” In October 2020, Giuliani turned the drive over to Delaware authorities, who in turn handed it over to the FBI.

The computer data that was turned over to the FBI showed no evidence of tampering or fabrication, according to an independent review commissioned by CBS News.

But in a letter, Lowell cited media reports indicating “[m]ore recently, downstream recipients of what has been purported to be Mr. Biden’s hard drive have reported anomalies in the data, suggesting manipulation of it.”

Among those Hunter Biden wants investigated are Garrett Ziegler, a former Trump administration aide, who was also the subject of a letter sent by Lowell to Robert Malone, the I.R.S’s director of tax exempt organizations. A limited liability corporation associated with Ziegler operates Marco Polo, a self-described nonprofit devoted to “exposing corruption” that has zeroed in on Biden’s laptop.

Lowell wrote that Marco Polo is “little more than a thinly disguised political operation to attack the Biden administration and the Biden family.”

The IRS did not reply to a request for comment. CBS News has also reached out for comment to a representatives for Marco Polo.

In another letter sent Wednesday, Biden attorney Bryan Sullivan demanded that Fox News and Tucker Carlson devote airtime to retracting statements made about Biden paying “rent” to his father, “in what Mr. Carlson implied was essentially a money laundering scheme to finance President Biden’s lifestyle prior to his election … and alluding to Mr. Biden having unauthorized access to classified documents because of his presence at President Biden’s house.” Sullivan writes that the claims were false, and even after others acknowledged as much, Carlson continued to make them.

The letter, which cites California’s defamation statute, notes that the Daily Caller website retracted an article that made similar claims.