Under the Constitution, Pence as vice president also served as president of the Senate, entitling him to some measure of congressional immunity, Boasberg found. Although Pence and his allies felt that the ruling didn’t extend far enough, Pence opted not to appeal the decision.

Trump’s executive privilege challenges to Justice Department subpoenas have not fared well in a series of secret court proceedings that have played out in recent months. He lost bids before Boasberg’s predecessor as chief, Beryl Howell, to prevent Pence’s aides from testifying in the inquiry, and he recently lost a similar bid to prevent his own top White House advisers from appearing for compelled testimony.

A Trump spokesman confirmed the appeal in a statement blasting the Justice Department’s handling of the special counsel investigations.

“The DOJ is continuously stepping far outside the standard norms in attempting to destroy the long accepted, long held, Constitutionally based standards of attorney-client privilege and executive privilege,” said Trump spokesman Steven Cheung. “The Special Counsel is conducting a witch-hunt where the government has sought to violate every Constitutional norm, including the safeguards that protect a President’s ability to confer with his Vice President on matters of the security of the United States.”

The appeal is one of more than 10 secret proceedings that have governed Smith’s expansive inquiries into Trump’s bid to subvert the election, as well as his handling of highly sensitive national security secrets found at his Mar-a-Lago estate after he left office. Grand jury proceedings typically play out in secret, a requirement of law and precedent, but the breadth and magnitude of these probes have led to extraordinary rulings that are reshaping the boundaries of the separation of powers, all outside of public view.

The appeals court’s secret docket reflects that Trump’s appeal was lodged Monday morning after a March 27 ruling by Boasberg in a grand jury matter — a date that coincides with Boasberg’s order for Pence to testify. Trump has not yet filed for an emergency expedited effort to block Boasberg’s ruling, but he has taken that step in several other cases to no avail.

It’s unclear when Pence is expected to testify, but typically judges set precise deadlines for compliance that may drive the timing of various filings and challenges.