House Speaker Nancy Pelosi warned that the Trump administration’s defiance of subpoenas could be an impeachable offense, even as the top White House lawyer instructed his predecessor not to comply with a subpoena from House Democrats.

White House Counsel Pat Cipollone said in a letter Tuesday to the House Judiciary Committee that President Donald Trump may want to assert executive privilege over the documents the panel is seeking from former counsel Don McGahn.

At the same time, Trump’s Justice Department is pushing back against a separate subpoena from the House Judiciary Committee for the full, unredacted version of Special Counsel Robert Mueller’s report.

Trump and his Republican allies are trying to move past the Mueller probe, with Senate Majority Leader Mitch McConnell calling it “case closed” in a floor speech Tuesday.

But Pelosi made clear that Democrats plan to press their multiple investigations of the president, accusing Trump of “goading” House Democrats into trying to remove him from office.

One of the articles of impeachment against President Richard Nixon was based on ignoring subpoenas from Congress, the speaker said Tuesday during an event at Cornell University.

“That could be part of an impeachable offense” against Trump, Pelosi said. “Every day he’s obstructing justice by saying this one should testify, that one shouldn’t testify.”

The Trump administration has been rebuffing House Democrats’ demands for testimony and documents, with Trump saying last month that “we’re fighting all the subpoenas.”

Questioning McGahn took on additional importance since the former White House counsel provided Mueller a detailed account about Trump’s attempt to have the special counsel removed from his post. The White House gave McGahn permission to speak with Mueller.

The House Judiciary Committee subpoenaed McGahn last month with a Tuesday deadline to comply with the records request. Cipollone told the committee to redirect its subpoena to the White House. His letter said White House acting Chief of Staff Mick Mulvaney instructed McGahn not to hand over the records.

A lawyer for McGahn, William Burck, said he told his client to honor the White House request, unless the committee and Trump administration reach an agreement.

Attorney General William Barr missed a separate deadline on Monday to comply with the Judiciary panel subpoena for the the full Mueller report on Russian election-meddling and the Trump campaign. After committee Chairman Jerrold Nadler scheduled a vote to hold Barr in contempt, the Justice Department agreed to hold further talks Tuesday on the dispute.

The House is justified in seeking the full Mueller report “in order to exercise all of the powers of Congress, including impeachment,” Pelosi said at Cornell.

Pelosi said following “the facts and the law” will lead Congress to the correct action to take in response to Trump’s actions documented in the Mueller report. She said any case against Trump must be built not only in congressional committees, but also in the court of public opinion.

“He is just trying to goad us into impeachment, and wherever you go, I say to my colleagues — whatever it is, be ready,” the California Democrat said.