Mexico-U.S. border wall prototypes/photo by CBP Photography/Flickr

Two starkly different legal views on President Donald Trump's moves to find funding for construction of barriers at the U.S.-Mexico border, a signature promise of his presidential campaign, were laid bare Tuesday morning at the U.S. Court of Appeals for the Ninth Circuit.

To the plaintiffs, a group of states and border nonprofits who sued separately to block funding, the administration violated the Constitution's Appropriations Clause when it reprogrammed military funds for border construction after being denied in the budget passed by Congress following a 35-day government shutdown.

"You can't build a wall without Congress, that's absolutely clear," said Douglas Letter, the top lawyer for the U.S. House of Representatives, arguing Tuesday as an amicus backing the plaintiffs.

Thomas Byron III, a lawyer with the Department of Justice's Civil Division arguing on behalf of the administration, meanwhile, argued that Congress had authorized the transfer of funds between Department of Defense accounts in a military spending bill passed earlier.

Byron said "it boggles the mind" that Congress could "somehow impliedly act" in a way that violated the express terms of a statute it previously passed.

The appeal springs out of cases brought by a group of Democratic states' attorneys general and nonprofit groups represented by the American Civil Liberties Union that were pending before U.S. District Judge Haywood Gilliam Jr. in Oakland. Gilliam issued orders in June and July blocking $2.5 billion in funding for the border barrier in certain locations in Arizona, California and New Mexico, finding that Congress hadn't authorized the administration to redirect funds to the appropriations account the Defense Department uses to fund its counternarcotic efforts.

A Ninth Circuit motions panel in July allowed Gilliam's injunctions to stay in place, but the U.S. Supreme Court later that month temporarily set the injunction aside until the Ninth Circuit could hear the merits of the case. The high court, voting along ideological lines, found that the administration made a sufficient showing that the plaintiffs did not have a cause of action to seek review of the decision to use Defense Department funds at the border.

At Tuesday's hearing, at least one member of the Ninth Circuit panel, Judge Daniel Collins, questioned whether the prior published motions panel was binding. Collins also questioned Byron about whether the prior panel had been correct in saying that the funds in question had been transferred from the Department of Defense to the Department of Homeland Security to proceed with border construction. Byron said that the earlier panel was incorrect and that the funds had merely shifted from one Defense Department account to another. Byron further argued that the sorts of "recreational, environmental, and aesthetic" harms alleged by the nonprofit plaintiffs weren't sufficient to establish standing to challenge a funding move expressly authorized in an appropriations statute.

Dror Ladin of the ACLU, arguing on behalf of the Sierra Club and a coalition of nonprofit groups along the border, said that his clients weren't attempting to invoke any sort of private right of action under the appropriation bill at issue, but were raising "core separation of powers issues that implicate private citizens." Ladin urged the court to decide the case "as expeditiously as it can" given the amount of construction that's already ongoing at the border.

James Zahradka of the California Department of Justice, arguing on behalf of the state plaintiffs, said that the administration had failed at argument and in its briefs to address the state's claims that their sovereign interests to enforce public health, environment, natural resources, and wildlife were at stake. "They really want to make this about this really technical government transfer," Zahradka said. "Congress has said that our state and local standards apply to federal construction projects."

Gilliam is one of three federal judges to consider a legal challenge to the administration's border wall funding maneuvers. In June, U.S. District Judge Trevor McFadden of the District of Columbia found that Congress did not have standing to sue the administration over border wall funding. In October, U.S. District Judge David Briones of the Western District of Texas found that the president violated federal law by declaring a national emergency in order to use more funds than Congress had appropriated.

Read more: 

Sidley Austin Presses US House's Legal Arguments in Trump's Border Wall Fight

Justices Will Let Trump Build Border Wall Without Congressional Funding

Judge: House Lacks Standing to Sue Trump Administration Over Border Wall Funding

Oakland Hearing Over Injunction to Block Border Wall Funding Serves as Run-Through for Top House Lawyer