A federal appeals court on Saturday temporarily allowed the construction of President Donald Trump’s White House ballroom to move forward while the administration challenges a lower court order that said the project exceeds the president’s authority.

The 2-1 decision by a three-judge panel for the U.S. circuit court in Washington, D.C., means construction can continue through April 17 while the court considers the issue in more detail. A lower court judge had previously ordered the construction to cease on April 14.

Trump’s lawyers have argued that the ballroom and other temporary measures are needed for “the safety and security” of the president, his family and others, according to the decision.

But the ruling said the appeals court could not “fairly determine, on this hurried record,” how these issues might affect the outcome of the case.

It sent the case back to the lower court with instructions to clarify these issues.

U.S. District Judge Richard Leon had previously sided with a preservation group that challenged the demolition and planned reconstruction of the East Wing of the White House, finding that the president needed congressional approval for the massive, $400 million project.

The administration had argued in a court filing that it’s a matter of national security for the construction to proceed at full steam, saying the “ballroom is clearly a vital project for the safety and security of the White House and the President, his family, and his staff.”

It also said Congress has no role in the construction.

“No taxpayer dollars are being used for the funding of this beautiful, desperately needed, and completely secure (for national security purposes) ballroom,” the filing said.

“Congress did not get involved with the design, planning, and architecture of either the original East Wing or the West Wing many decades ago,” it said. “Decisions about what is needed to keep the President, his family, and his staff safe rest with the President, and cannot possibly be outsourced to other branches of government, just as the President could not dictate the Senate’s building needs or architectural design.”

The National Trust for Historic Preservation, which is challenging the project, told the appeals court in a filing that congressional approval is required for construction projects on federal property — and that the administration’s security concerns are overblown.

“Defendants appear to contend that being prevented from illegally constructing a massive ballroom constitutes a national security emergency. It plainly does not,” the organization said.

It noted that the ballroom is expected to take at least two years to build, and “the absence of a massive ballroom on White House grounds has not stopped this (or any other) President from residing at the White House or hosting events there.”

On Saturday, National Trust President and CEO Carol Quillen applauded the appeals court decision.

“We appreciate the court of appeals acting quickly and await further clarification from the district court,” she said in a statement. “The National Trust remains committed to honoring the historic significance of the White House, advocating for our collective role as stewards, and demonstrating how broad consultation, including with the American people, results in a better overall outcome.”

Leon, a George W. Bush appointee, issued the preliminary injunction after finding the trust was “likely to succeed on the merits because no statute comes close to giving the President the authority he claims to have.”

The president, Leon wrote, is the “steward of the White House for future generations of First Families.”

“He is not, however, the owner!” Leon added.

The ballroom has been a passion project for Trump during his second term. He has been heavily involved in the planning, repeatedly showing off models of the site to reporters, and has made repeated references to it when he speaks about other topics, including the war with Iran.

When he first announced the project, he said it wouldn’t “interfere” with the current building, but he then had the East Wing demolished, saying it was not in good shape and needed to be torn down and modernized.

Trump has said the ballroom is necessary to allow the administration to host foreign leaders and large indoor events, rather than use makeshift tents on the South Lawn.

The Justice Department touted a number of security features and construction materials that have already been purchased to highlight the project’s importance to the appeals court.

“As an example, the protective missile-resistant steel columns, beams, drone proof roofing materials, and bullet, ballistic, and blast proof glass, are largely made, being used, and/or on their way to the project,” the filing said. “Likewise, the bomb shelters, hospital and medical area, protective partitioning, and Top Secret Military installations, structures, and equipment, are built and/or ready to be built, installed, and placed.”

The preservation group countered that most of those items were believed to be being installed underground, and Leon’s injunction “does not prevent Defendants from working on the underground bunker their motion exhaustively describes; indeed, the Trust has never objected to that.”

It noted that the administration argued in court filings last year that the underground work was separate from the ballroom work — but once the judge’s ruling was handed down, “the ballroom and bunker suddenly (and conveniently) became inseparable.”

“Only when someone stopped their illegal ballroom did the previously acceptable status quo become a supposed ‘national security’ crisis overnight,” the trust said.

Trump told reporters in late March that the military was building a “massive complex” underground, and “the ballroom essentially becomes a shed for what’s being built under.”