Harlan Crow, a billionaire Republican donor, has refused a second request by Senate Finance Committee Chairman Ron Wyden to answer questions about gifts and travel he provided to Supreme Court Justice Clarence Thomas.

The committee doesn’t have authority to make demands about Crow’s friendship with Thomas when other sources could provide Congress the information, Crow’s attorney Michael Bopp said in a letter obtained by Bloomberg News. Wyden sent his letter to Crow on May 17.

“A desire to focus on Justice Thomas, not the intricacies of the gift tax, appears to have been the genesis of this Committee inquiry. But ‘there is no congressional power to expose for the sake of exposure,’” Bopp wrote.

Bopp also said the committee lacks jurisdiction to demand that Crow provide the disclosures.

“The letter fails to establish a valid justification for the Committee’s impermissible legislative tax audit of a private citizen, Mr. Crow, nor does it identify any legitimate legislative need for requesting additional information from Mr. Crow in light of the legislative initiatives that the Committee suggests it may be pursuing,” Bopp said.

Over two decades, Crow paid for vacations for Thomas and his wife, including trips on a yacht and private jet, ProPublica has reported. Thomas, who hadn’t disclosed the travel, later amended his disclosure and defended his decision to not document the trips.

Democrats who control the Senate have been stepping up inquiries after ProPublica reported in April that Thomas failed to disclose lavish trips and gifts from Crow. Democrats are pushing for probes into the matter, while Republicans are pushing back and calling it a ‘ploy.’

Read more: Benefactor to Justice Thomas Refuses to Answer Senate Inquiry

Crow has refused to answer similar requests from Senate Judiciary Committee members, who asked for details of gifts or payments made to Thomas or the other high court justices.

Democrats on both committees have authority to issue subpoenas. Wyden’s jurisdiction also includes the ability to obtain individual tax returns from the IRS as part of its investigations.

Wyden wrote in a response to Crow’s first rejection that the Senate has the right to obtain a response from Crow, arguing that the Finance Committee has jurisdiction over tax policy.