Former Trump White House counsel Donald McGahn must comply with a House subpoena, a federal court ruled Monday, finding that “no one is above the law” and that top presidential advisers cannot ignore congressional demands for information. The ruling raises the possibility that McGahn could be forced to testify as part of the impeachment inquiry.

U.S. District Judge Ketanji Brown Jackson of Washington found no basis for a White House claim that the former counsel is “absolutely immune from compelled congressional testimony,” setting the stage for a historic separation-of-powers confrontation between the executive and legislative ­branches of the ­government.

The House Judiciary Committee went to court in August to enforce its subpoena of McGahn, whom lawmakers consider the “most important” witness in whether President Trump obstructed justice in special counsel Robert S. Mueller III’s investigation of Russian interference in the 2016 U.S. election.

Trump blocked McGahn’s appearance, saying McGahn had cooperated with Mueller’s probe, was a key presidential adviser, and could not be forced to answer questions or turn over documents. Jackson disagreed, ruling that if McGahn wants to refuse to testify, such as by invoking executive privilege, he must do so in person and question by question.

The Justice Department’s claim to “unreviewable absolute testimonial immunity,” Jackson wrote, “is baseless, and as such, cannot be sustained.”

The judge ordered McGahn to appear before the House committee and said her conclusion was “inescapable” because a subpoena demand is part of the legal system — not the political process — and “per the Constitution, no one is above the law.”