“President Trump’s arguments in the impeachment trial contradict DOJ’s assertion in this case that the Committee may not seek to enforce its subpoenas in court,” Letter said.

Don McGahn, former White House counsel. | Drew Angerer/Getty Images

A three-judge panel from the D.C. Circuit is expected to rule any day now in a case involving the House Judiciary Committee’s monthslong fight to subpoena testimony from Don McGahn, the former White House counsel. McGahn served as a star witness in the Russia inquiry, meeting for 30 hours with special counsel Robert Mueller’s investigators and sharing details about Trump’s efforts to stymie and kill the probe into Russian interference in the 2016 presidential election.

Democrats approved a subpoena for McGahn last spring, but Justice Department lawyers blocked his compliance, prompting a drawn-out court fight that culminated in November with a decision from a federal judge in favor of the House. The department appealed the case to the D.C. Circuit, arguing both that McGahn and other government officials enjoy absolute immunity from testifying and also that the courts shouldn’t meddle in these kinds of disputes.

The McGahn legal dispute has taken a back seat to the current House-led impeachment push, which centers on Trump’s attempts to pressure Ukraine into launching investigations into his political opponents. But House Democrats haven’t let go of the McGahn case, either, and their lawyers have said in court that they could use any evidence uncovered if they secure a win either in the Senate trial or by pursuing additional impeachment articles against Trump.

Against that backdrop and with the McGahn case still pending, House lawyers seized on remarks Sekulow made on Tuesday during the impeachment trial that appeared to undercut the Justice Department’s claims in court. On the Senate floor, Sekulow said, “The president’s opponents, in their rush to impeach, have refused to wait for judicial review.”

Letter’s response: “In light of President Trump’s argument, it is not clear whether DOJ still maintains its position that courts are barred from considering subpoena-enforcement suits brought by the House. At the very least, President Trump’s recognition that courts should resolve such suits undermines DOJ’s contrary threshold arguments in this case, which seek to prevent the House and its committees from seeking judicial resolution of subpoena-enforcement disputes.”

“The Executive Branch cannot have it both ways,” Letter added.

A senior DOJ official swung back Friday morning in an email at the House Democrats' letter claiming Sekulow had undercut the president's case. "This is an entirely contrived conflict," the official said.

The official pointed to language in the president's legal brief filed to the Senate in the impeachment trial earlier this week that "agrees with and embraces the department's long-standing view that the House cannot use the courts as enforcers of subpoenas against the Executive Branch."

"All the president's team is arguing is that the House cannot have it both ways," the DOJ official added.

By early Friday afternoon, deputy assistant attorney general Hashim Mooppan had put into writing DOJ's objections about the House's "unprecedented commingling" of using a lawsuit to back Trump's removal from office.

"We previously warned that the House seeks to use this litigation to support impeachment," Mooppan wrote in a two-page response to the D.C. Circuit. "Now, the Committee seeks to use the impeachment proceedings to support this litigation."

Democrats on Thursday also sent a letter to the D.C. Circuit in a second impeachment-related case tied to their long-standing attempts to learn Mueller’s grand jury secrets.

In that letter, they informed the court about the start of the Senate impeachment trial this week and urged it to rule “expeditiously” on whether impeachment investigators can see all of the blacked-out words, phrases, sentences, paragraphs and entire pages in the version of the Mueller report released last April summarizing his investigation.

“It is difficult to conceive of a public interest more substantial than ensuring that the House obtains highly pertinent evidence to present to the Senate as it considers whether the President should be removed from office,” Letter wrote.

Two different D.C. Circuit panels heard arguments earlier this month in both the McGahn and Mueller grand jury cases.

Kyle Cheney contributed to this report.