WASHINGTON, Nov. 25 (Xinhua) -- A U.S. federal judge ruled here Monday that former White House counsel Don McGahn must comply with a subpoena issued by the House and testify before Congress.

"However busy or essential a presidential aide might be, and whatever their proximity to sensitive domestic and national-security projects, the President does not have the power to excuse him or her from taking an action that the law requires," Ketanji Brown Jackson, a U.S. district court judge, said in her 118-page decision.

"Presidents are not kings," wrote Jackson. "No one, not even the head of the Executive branch, is above the law."

McGahn was subpoenaed in April by House Judiciary Committee Chairman Jerry Nadler, a Democrat from the state of New York, months before the start of the impeachment inquiry.

The Justice Department, which is representing McGahn in the lawsuit, earlier said that the counsel could not be compelled to appear before Congress, adding that the president and his immediate advisers are immune to such demands.

Jackson said McGahn must appear before Congress but still retains the ability to "invoke executive privilege where appropriate" during his appearance.

The judge didn't say whether she will put her ruling on hold for the administration to appeal.

U.S. media reported that the Justice Department will appeal Jackson's decision, and seek a court stay to prevent McGahn from speaking.