FIRST ON FOX: Conservative judicial activist Leonard Leo has again rejected demands from Senate Democrats as they seek to gather information as part of their ongoing investigation into conservative Supreme Court justices, Fox News Digital has learned.

Senate Judiciary Committee Democrats Dick Durbin of Illinois and Sheldon Whitehouse of Rhode Island have sent two letters to Leo and billionaire activists in recent months summoning information regarding trips and events that Supreme Court justices have taken and participated in over the years.

On October 5, the senators sent the second letter to Leo, Harlan Crow and Robin Arkley in an attempt to strong-arm them into complying with a previous July request for details about trips involving Justices Clarence Thomas and Samuel Alito.

However, Leo soundly rejected their demands on Friday in a letter his attorneys sent to committee chairman Durbin, a copy of which Fox News Digital has obtained.

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Sheldon Whitehouse, Dick Durbin

Sens. Sheldon Whitehouse, left, and Dick Durbin, right, have been attempting to get information from judicial activist Leonard Leo as part of their investigation into conservative Supreme Court justices. (Getty Images)

"We have put forward clear and detailed reasons why the Committee's inquiry is a form of political retaliation in violation of the First Amendment and the Equal Protection component of the Due Process Clause," Leo's attorney, David Rivkin, wrote in the letter. "But, for the most part, the October 5 Letter ignores these points, and, since our last correspondence, the Committee has only expanded the retaliatory campaign it is mounting against Mr. Leo."

"We also have explained at length why the Supreme Court ethics legislation the Committee has written would violate the separation of powers if enacted, and thus cannot legitimate the Committee’s inquiry," Rivkin said. "But the October 5 Letter offers virtually nothing in the way of rebuttal, and the Committee continues to press forward with its unconstitutional bill. Across the board, the October 5 Letter tries to shield the Committee’s inquiry from our objections by simply acting as though they do not exist."

Rivkin added that they believe the Senate Judiciary Committee "is not entitled to the personal information it seeks" and, because they have not provided "arguments to the contrary," declined to provide the information.

The senators have requested an itemized list of gifts and payments from Leo or his linked groups dating back decades in relation to any Supreme Court justice he has associated with, as part of their investigation.

"The latest response by Leonard Leo and Republican megadonors is a defensive, dismissive refusal to inform legislative efforts to establish a code of conduct for all Supreme Court Justices," a Durbin spokesperson told Fox News Digital.

"This effort is squarely within the Committee’s jurisdiction, popular among the American people, and necessary to re-establish trust in the Supreme Court," the spokesperson said. "So long as Chief Justice Roberts refuses to use his power to implement a code of conduct, Congress will continue to act. Chair Durbin and Senate Judiciary Democrats are considering next steps, and all options remain on the table."

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Sen. Dick Durbin, D-Ill.,

Sen. Dick Durbin, D-Ill., speaks with reporters on Capitol Hill, Wednesday, April 19, 2023, in Washington.  (AP Photo/Alex Brandon, File)

For decades, Leo has been a part of the Federalist Society, which has long been criticized by liberal activists for its involvement in helping advise and lobby former President Trump through the nominations of Supreme Court Justices Gorsuch, Brett Kavanaugh and Amy Coney Barrett.

The senators' demands stem from ProPublica's reporting on the travel habits of Justices Thomas and Alito, which conservatives have widely criticized by pointing out that many of the "experts" cited in the various reports have undisclosed ties to Democratic causes.

Conservatives have called out ProPublica for being primarily funded by organizations and donors who support liberal causes, including court-packing and removing conservative justices from the court.

Alito has defended himself against ProPublica's reporting, and Leo has released a statement dismissing the idea that the fishing trip was somehow kept from the public.

"Justice Alito talked about this trip in front of dozens of journalists and over 2,000 people after being introduced by Paul Singer at a Federalist Society dinner fourteen years ago," Leo said in a prior statement. "Nobody questioned Justice Alito’s impartiality then, or thereafter."

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Sen. Whitehouse

Sen. Sheldon Whitehouse, D-R.I., leaves the Senate Democrats lunch in the Capitol on Tuesday, June 13, 2023.  (Bill Clark/CQ-Roll Call, Inc via Getty Images)

Leo added that "the only thing that has changed over all these years is that ProPublica and its large pool of liberal dark money donors are having a hard time accepting the fact that they are now losing cases because there aren’t enough Justices around anymore to disregard the law and affirm their policy preferences."

Supporters of Thomas have insisted that he has broken no laws or ethics codes. 

Meanwhile, Leo has also come under the microscope of Washington, D.C.'s Democrat attorney general Brian Schwalb, who launched an investigation into Leo's network this past summer. 

Schwalb's office faced criticism for targeting Leo while ignoring a similar liberal dark money network overseen by the Arabella Advisors consulting firm. 

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However, after the criticism, Schwalb's office also opened a probe into the Arabella Advisors-managed network.