An en banc federal appeals court Tuesday indicated it will rule in favor of the House's ability to go to court against the executive branch, as it heard arguments over the significant legal question that's sure to land before the U.S. Supreme Court.

Judges on the U.S. Court of Appeals for the D.C. Circuit pressed Justice Department appellate attorney Hashim Mooppan over the administration's stance that the House lacks both the ability to sue Trump administration officials or arrest them under its inherent contempt powers. They also questioned House general counsel Douglas Letter about whether lawmakers actually could challenge a presidential order that redirected military funds for border wall construction, and how they could narrow that ruling.

At the same time, the judges made clear they felt the gravity of their upcoming opinions. Any decision is certain to have far-reaching consequences for the House's tranche of legal challenges already sitting within the circuit, as well as federal judges' ability to preside over disputes between the two other branches.

"These cases, both of them, are sort of big deals," said Judge Patricia Millett. "It seems like a decision either way may not be fairly described as neutral in these cases."

"If the court goes with the Justice Department, you will basically make an enormous change to congressional oversight as it's been known in this country for years," Letter replied, adding that it could also substantially shift the separation of powers.

Those concerns reverberated within the judges' questions to both Letter and Mooppan during the three-hour arguments. The hearing was only the second time the D.C. Circuit has heard en banc arguments telephonically, with Monday's session marking the first. The judges asked questions one at a time Tuesday, in order of seniority, with Chief Judge Sri Srinivasan choosing to go last.

The arguments centered on a pair of House lawsuits: One seeking to enforce a subpoena for former White House counsel Don McGahn's testimony, and another on President Donald Trump's diversion of Pentagon funding for border wall construction. A D.C. Circuit panel ruled earlier this year in the McGahn case that the House couldn't go to court to enforce the subpoena; the three-judge panel on the border wall case did not issue an opinion before the en banc rehearing.

Mooppan told the judges they should uphold the original panel opinion issued by the circuit on the House's inability to sue to enforce congressional subpoenas in the case involving McGahn. Mooppan argued only the executive branch has the power to seek judicial enforcement of the subpoenas, as it represents the United States in court, and that political branches should use political tools to resolve their disputes.

"That is what ambition checking ambition is all about, and it totally overrides all of that to say if Congress is upset its subpoenas aren't complied with or its statutes aren't complied with," it can go to court, Mooppan argued.

But those claims were often met with resistance from the judges, who seemed wary of completely cutting off the House from judicial enforcement of subpoenas.

Judge Merrick Garland posed a number of hypotheticals to Mooppan, including whether Congress could sue if a president ordered his administration to provide health care to all Americans who could not get private insurance. Mooppan, sticking with the argument there is no situation where Congress can sue the executive branch, said the lawmakers could not.

"That's a significant power that the president has that can't be checked by the Congress," Garland said at one point.

Judge Thomas Griffith, who wrote the McGahn opinion, later asked Mooppan, "How is Congress to conduct its constitutional duty of oversight in the face of the type of utter disregard this administration has shown for that oversight?" He cited Trump saying his administration would "fight all the subpoenas" during last year's impeachment inquiry.

Mooppan said there was "never a blanket edict" to defy congressional subpoenas, including oversight ones, while acknowledging the administration found the impeachment subpoenas to be "categorically improper."

Judge Judith Rogers, who dissented in the panel opinion on McGahn, seemed particularly dubious of the Justice Department's arguments.

"Are you not struck by the fact that in these two cases that what is at stake is the separation of powers and the balances of these powers, and deciding that on standing itself implicates those powers?" she asked of Mooppan.

"I've yet to hear anyone identified who would have standing as private individuals if, in a hypothetical situation, the president … in his first year of office redoes the separation of powers, as some of Judge Garland's hypotheticals were suggesting," Rogers later said. "There's nothing that could be done until the next presidential election other than revolution?"

There was also a tense moment between Millett and Mooppan, after he said the judge "misread" a footnote in an opinion she was citing. "I read it word for word," Millett rebutted, and Mooppan later clarified he meant misreading the footnote within the context of the opinion.

The judges questioned Mooppan for nearly twice as long as Letter. Some sitting on the panel asked the Justice Department attorney questions during a follow-up round, but none of the judges did the same for the House lawyers.

During Letter's time, the judges focused their questions on cases when he believed the House could or could not sue, such as a president declaring war without authorization from Congress.

They also pressed Letter about what kind of ruling they should make on the border wall case, including if they should limit their finding to solely this matter. They also took issue with Letter's assertion that the Constitution's Appropriations Clause has a "special impact" in the lawsuit.

Letter told the judges that the circumstances surrounding the border wall funding were "extraordinary," and was unlikely to result in a flood of litigation from the House challenging other administration policies.

"This is one of those rare cases where the House has a concrete institutional injury," he said, adding that it's "extremely unlikely there will be other appropriate cases that will be cognizable."

Missing from Tuesday's panel were Trump's two appointees to the circuit, Judges Gregory Katsas and Neomi Rao. Both have not weighed in on the McGahn lawsuits, suggesting both former Trump administration officials have recused.

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