WASHINGTON – The Trump administration faced tough questioning Tuesday from a federal appeals court over its refusal to let former White House counsel Donald McGahn testify before Congress and its spending on a border wall without congressional approval.

The U.S. Court of Appeals for the District of Columbia Circuit, the nation's second most powerful court, combined the two disputes into a single, three-hour oral argument because both deal with the separation of powers between the legislative and executive branches of government.

"These cases, both of them, are sort of big deals," Judge Patricia Millett said near the end of the argument, which, like most federal and state court hearings right now, was held by telephone conference because of the coronavirus pandemic.

The administration thus far has held the upper hand in both battles. It blocked McGahn from testifying about potential obstruction of justice by Trump during the investigation of Russian interference in the 2016 election, and it moved ahead with some $6 billion in emergency border wall spending that Congress did not approve.

But the appeals court, dominated by Democratic presidents' nominees, expressed skepticism on both counts.

In the McGahn case – one of multiple, lingering congressional probes of Trump and his administration – Judge Judith Rogers said that under the Justice Department's theory that Congress cannot subpoena testimony, "there's nothing that can be done until the next presidential election, other than revolution."

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In the border wall funding case, which has been fought in federal courts from California to Texas to Washington, D.C., Judge Merrick Garland said that if the executive branch can "just (give) money away ... that’s a significant power that the president has that can’t be checked by Congress.”

A three-judge appeals court panel ruled in February that McGahn does not have to testify, saying the court can't be an "ombudsman" between the two other branches. The full court then agreed to rehear the case.

Similarly, U.S. District Court Judge Trevor McFadden ruled last June that the House did not have judicial standing to file its border wall funding lawsuit, and a three-judge panel kicked the matter to the full court.

In both cases, the Justice Department argued that the judiciary should not resolve disputes between the other two branches. Assistant Attorney General Hashim Mooppan argued Tuesday that it "would be a radical break from tradition" for federal courts to adjudicate inter-branch disputes. Doing so "would politicize the judiciary," he said.

When various judges pressed Mooppan about why the judiciary cannot intervene and what options are left for Congress to enforce its authority, he said Congress has "ample" political tools, including cutting funding and hindering presidential nominations.

Douglas Letter, general counsel for the House of Representatives, said the claim that there is no precedent for government branches suing each other is "absolutely not true." Courts routinely resolve those cases, he said.

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Letter said the Trump administration has left Congress with no other option but to turn to the courts, citing comments by the president during special counsel Robert Mueller's investigation into Russian election interference that he would fight all congressional subpoenas. Political alternatives "are not practical" and have "simply failed to work" with the Trump administration, Letter said.

During impeachment proceedings last year, when Democrats subpoenaed several witnesses to testify about the administration's dealings with Ukraine, the president's lawyers told lawmakers that they should turn to the courts to enforce those subpoenas, Letter noted.

“If we can’t enforce subpoenas, then they become really like a joke,” Letter said, later adding, “Maybe we could have gun battles between the (House) sergeant-at-arms and the attorney general's security detail.”