The move comes as House investigators have begun releasing damaging closed-door testimony from State Department officials implicating Giuliani in the White House's decision to block military aid for Ukraine unless it announced investigations into the Biden family and 2016 election interference.

As Giuliani alluded to in his tweets, he has set out to prove that the Justice Department and the entirety of the U.S. intelligence community were wrong in their conclusion that Russia interfered in the 2016 election to boost Trump, making the unfounded assertion that Ukrainians were behind the meddling instead.

And Giuliani’s announcement comes hours after House Intelligence Chairman Adam Schiff (D-Calif.) revealed that the first public hearings in the impeachment inquiry would kick off next week.

House Intelligence Chairman Adam Schiff (D-Calif.) revealed that the first public hearings in the impeachment inquiry would kick off next week. | Drew Angerer/Getty Images

Giuliani had been subpoenaed for documents by House investigators for their impeachment inquiry, but said he would not comply, calling their impeachment investigation illegitimate and claiming attorney-client and executive privilege. He was briefly represented by a former Watergate prosecutor and law school classmate for purposes of responding to the subpoena, but after informing investigators he would not turn over the requested records, Giuliani told POLITICO he was lawyer-less.

But the former New York mayor is also reportedly in legal hot water of his own. The New York Times reported last month that Giuliani was under federal investigation tied to his efforts to undermine Marie Yovanovitch, the U.S. ambassador to Ukraine who was recalled in the spring amid a wider campaign to pressure the country’s leaders into investigating Trump’s political opponents.

Two of Giuliani’s associates in his Ukraine efforts were indicted last month on campaign finance violations, and on Monday, lawyers for one of the men, Lev Parnas, said he might be willing to cooperate with impeachment investigators.

While federal prosecutors have not confirmed the existence of a Giuliani-specific investigation, the Wall Street Journal reported last month on the existence of a grand jury that subpoenaed former GOP Rep. Pete Sessions for documents related to Giuliani’s Ukraine business and interactions with Giuliani’s indicted associates.

Deposition transcripts released by House investigators all week have shown Giuliani to be a constant presence in that campaign, which Giuliani himself has acknowledged playing a role in.

Robert Costello, one of the lawyers Giuliani announced would represent him, has been involved with the legal troubles ensnaring the White House at least once before. He cropped up during the legal proceedings of Michael Cohen, Trump’s onetime personal attorney and fixer, in what appeared to be conversations about a potential pardon.

Costello had reportedly told Cohen via email that he was in contact with the White House by way of a “back channel,” which was Giuliani.

“I spoke with Rudy,” Costello wrote Cohen in April 2018. “Very Very Positive. You are ‘loved.’”

According to emails Cohen shared with the House Intelligence Committee, Costello told Cohen to “sleep well tonight, you have friends in high places.” Cohen told lawmakers he believed Costello was referring to Trump.

Cohen is currently serving a three-year prison sentence for perjury, campaign-finance violations, and tax and bank fraud crimes.

