WASHINGTON — A US appeals court judge ruled Monday that President Donald Trump's top aides must comply with subpoenas issued by the impeachment investigation against him.

In a case involving former White House counsel Don McGahn, who was subpoenaed in May by the House Judiciary Committee, judge Ketanji Jackson ruled that administration officials cannot claim absolute immunity from testifying based on their closeness to the US leader.

While Jackson ruled specifically on McGahn's case, she said it had broad application to all current and former presidential aides.

"Presidents are not kings," Jackson wrote in her decision. 

"No one, not even the head of the Executive branch, is above the law."

She said Congress has the power to subpoena any of the president's advisors, whether they are involved in domestic policies or sensitive national security issues.

"It goes without saying that the law applies to former White House Counsel Don McGahn, just as it does to other current and former senior-level White House officials," she wrote.

That ruling could open a path for the House Intelligence Committee – which is building a case for impeachment charges against Trump – to force testimony from three top witnesses: former national security advisor John Bolton, White House Chief of Staff Mick Mulvaney and Secretary of State Mike Pompeo.

All are believed to have direct knowledge of Trump's alleged demand that Ukraine President Volodymyr Zelensky open investigations into Trump's Democratic rivals in exchange for a high profile summit and much-needed military aid. — AFP