A U.S. judge on Tuesday ordered a stop to construction of President Donald Trump’s planned White House ballroom, which has already involved the demolition of the historic East Wing.

Trump, a billionaire real estate developer, is “steward” of the White House but “he is not, however, the owner!” wrote Judge Richard Leon, saying congressional approval is required for the project.

The ruling came after a legal challenge from the National Trust for Historic Preservation, a nonprofit that seeks to protect historic buildings.

“He’s so wrong,” Trump told reporters in the Oval Office Tuesday, insisting Congress did not need to be involved because the project is to be funded by donors, not taxpayers.

His administration filed an appeal hours after Leon’s decision.

Trump drew criticism last year when a section of the White House was bulldozed to make way for the ballroom, which he has described as necessary for large-scale events. He frequently highlights the project in speeches and on social media, calling the National Trust “a Radical Left Group of Lunatics” and describing the ballroom as “the finest Building of its kind anywhere in the World.”

The project, initially estimated at $200 million and now expected to cost up to $400 million, is reportedly funded by private donors, including wealthy supporters and corporations.

Leon’s opinion said the decision rests with Congress, which must also determine funding. “Ballroom construction project must stop until Congress authorizes its completion,” he wrote, giving a two-week delay to allow for an appeal.

“No statute comes close to giving the president the authority he claims to have,” Leon added. “The President may at any time go to Congress to obtain express authority to construct a ballroom and to do so with private funds. Indeed, Congress may even choose to appropriate funds for the ballroom. Either way, Congress will thereby retain its authority over the nation’s property and its oversight over the Government’s spending.”

The ballroom would be Trump’s most prominent mark on the U.S. capital since returning to office in January 2025. His tenure has also included extensive modifications to the Oval Office, Rose Garden, and the Kennedy Arts Center.