White House Counsel Don McGahn listens to Judge Brett Kavanaugh as he testifies before the Senate Judiciary Committee during his Supreme Court confirmation hearing in the Dirksen Senate Office Building on Capitol Hill in Washington, U.S., September 27, 2018. Win McNamee/Pool via REUTERS

U.S. District Judge Ketanji Brown Jackson in Washington said she would rule by Monday in a lawsuit by a U.S. House of Representatives committee seeking to compel former White House Counsel Don McGahn to testify in the probe.

Brown Jackson, an appointee of former President Barack Obama, suggested during oral arguments in October that she would rule in favor of the House. The Trump administration has argued that the U.S. Constitution does not give Congress power to compel testimony from senior members of the executive branch.

A judge rejected a similar argument in 2008 in a fight over a subpoena issued to former President George W. Bush’s White House counsel.

A decision that McGahn must testify would not bind other officials and would almost certainly be appealed. But some lawyers said Bolton and others could use a ruling to justify talking to Congress if they decide doing so would be in their self-interest.

This month, Bolton’s lawyer said in a letter that Bolton “stands ready” to testify if a judge ruled that Congress has the authority to make him appear. However, Bolton did not appear for a closed-door deposition on Nov. 7.

“It could be a warm embrace for those who want to testify but need a reason to do,” said Jessica Levinson, a law professor at Loyola Law School in Los Angeles. “It would give political cover to those who want to come forward.”

Bolton’s lawyer Charles Cooper did not respond to a request for comment on Brown Jackson’s forthcoming ruling. William Burck, a lawyer for McGahn, declined to comment.

The Democratic-controlled U.S. House of Representatives is investigating whether Trump abused his power by pressing Ukraine to carry out investigations that would benefit him politically, including one targeting political rival Joe Biden.

Trump and his supporters have attacked the impeachment probe as politically motivated and called it a witch hunt.

A string of public impeachment hearings ended on Nov. 21, but House leaders have not ruled out conducting more hearings before they vote on whether to charge Trump. Additional witnesses could be called in a Senate trial to determine Trump’s guilt or innocence.

Some high-ranking diplomats in the State Department and White House National Security Council officials have cooperated with the House investigation, defying Trump’s orders.

Others, including McGahn, Bolton, Secretary of State Mike Pompeo, and Acting Chief of Staff Mick Mulvaney, have so far refused to testify.

Bolton and one of his former aides, Charles Kupperman, did not show up for closed-door depositions earlier this month. But Bolton has hinted that he has a story to tell to investigators.

Earlier this month, Bolton’s lawyer said in a letter to the House’s counsel that his client was “personally involved” in events and meetings under investigation, and knew about “many relevant meetings and conversations” that lawmakers may not be aware of.

Bolton has joined a lawsuit filed by Kupperman seeking a court ruling on whether he must comply with a congressional subpoena.FILE PHOTO – White House former National Security Advisor John Bolton delivers remarks on North Korea at the Center for Strategic and International Studies (CSIS) think tank in Washington, U.S. September 30, 2019. REUTERS/Jonathan Ernst

That lawsuit, which is before U.S. District Judge Richard Leon, could be dismissed on procedural grounds, potentially making the McGahn battle more significant.

A ruling for the House in the McGahn case “is a definitive ruling that the House is entitled to testimony” from current and former senior executive branch officials, said Paul Rosenzweig, a former Justice Department lawyer.

“They are not parties to the case, but the principle applies,” said Rosenzweig, now a senior fellow at the libertarian R Street Institute. “The question is if they even want to talk.”