Chairman of the House Oversight Committee Rep. Elijah Cummings (D-Md.) is threatening to hold former White House official Carl Kline in contempt after he did not appear on Tuesday for his deposition. Kline was called to testify in the panel’s White House security clearance investigation.

Cummings says that Kline’s actions “stand in open defiance of a duly authorized congressional subpoena with no assertion of any privilege of any kind.” If Democrats follow through on the threats,  Kline will be the first Trump Administration official to be held in contempt of Congress.

Depending on the nature of the contempt citation, this could allow congressional leaders to seek criminal charges against him, or refer his refusal to comply with a subpoena to the Justice Department for prosecution.

Robert Driscoll, Kline’s attorney, said his client takes the matter seriously, but questions the validity of the subpoenas.

“My client and I take seriously the concerns of the Committee and the Chair,” Driscoll said in a statement. “We also take seriously the direction of the White House not to attend today’s hearing and the opinion, expressed by the Department of Justice Office of Legal Counsel, about the validity if the Committee’s subpoenas given the restriction placed by the Committee. Chairman Cummings is zealously playing the role he should in our constitutional system and we bear no ill will towards him. We will continue to review the proceedings and make the best judgments we can.”

Kline, who now works in the Defense Department, was accused by a whistleblower of granting high level security clearance to Jared Kushner and other White House officials while he served as the White House personnel security director against recommendations of administration security specialists.

The White House has not responded for comment, but Driscoll said Kline was instructed not to appear before the committee by the White House.

“With two masters from two equal branches of government, we will follow the instructions of the one that employs him,” Driscoll wrote in a letter to the committee.