Former White House lawyer Don McGahn refused to comply with a subpoena to testify before the House Judiciary Committee on Tuesday about special counsel Robert Mueller’s Russia report, setting the stage for the panel to hold him in contempt.

As Rep. Jerrold Nadler, the chairman, gaveled the committee into session, a chair where McGahn was expected to sit during his appearance remained empty.

McGahn, who left the White House in October, was a star witness in Mueller’s 448-page report and described how President Trump had ordered him to have the special counsel fired.

The White House on Monday told McGahn to ignore the subpoena because he has “absolute immunity” as a former member of the administration and adviser to the president.

White House lawyers pointed to a Department of Justice legal opinion on the matter.

The immunity “extends beyond answers to particular questions, precluding Congress from compelling even the appearance of a senior presidential adviser – as a function of the independence and autonomy of the president himself,” Assistant Attorney General Steven Engel wrote in the 15-page opinion.

McGahn’s lawyer later confirmed that McGahn would abide by the White House’s request.

“Mr. McGahn remains obligated to maintain the status quo and will respect the President’s instruction,” William Burck wrote in a letter that called for the committee and the White House to negotiate a solution.

Nadler warned McGahn that he will “face serious consequences if you do not appear.”

“It is absurd for President Trump to claim privilege as to this witness’s testimony when that testimony was already described publicly in the Mueller report,” he said in a statement. “Even more ridiculous is the extension of the privilege to cover events before and after Mr. McGahn’s service in the White House.”

The White House’s refusal to comply with the subpoena further complicates a standoff between congressional Democrats and the White House over continuing investigations into Trump and his administration.

Earlier this month, the House Judiciary Committee held Attorney General William Barr in contempt for refusing to turn over a full, unredacted version of the Mueller report to Congress.

Trump had claimed executive privilege over the contents of the report and any underlying evidence.

In his report, Mueller said investigators did not find evidence of a criminal conspiracy between the Trump campaign and the Russians during the 2016 election.

But he didn’t reach a conclusion on whether Trump obstructed justice, leaving the decision to Congress and including 10 instances in which the president tried to derail the probe.