The National Trust for Historic Preservation, a nonprofit based in Washington, has filed a lawsuit seeking to block the Trump administration’s plan to build a large new ballroom attached to the White House’s east wing, Al Jazeera reported. The legal challenge, filed on Friday, targets one of President Donald Trump’s major renovation projects: a proposed 90,000-square-foot expansion to the White House complex.

Preservation advocates have long criticized the project, arguing that it compromises the historic character of the building and that the administration bypassed proper review procedures. This lawsuit represents the first formal legal attempt to halt construction. “Given the White House’s status as a key symbol of American ideals, the National Trust felt compelled to step in,” said National Trust President Carol Quillen, according to Al Jazeera. “As the organization responsible for protecting sites of historical significance, filing this case was necessary.”

The lawsuit claims the administration violated multiple rules, including failing to submit construction plans to the National Capital Planning Commission, skipping an environmental assessment, and neglecting to obtain congressional approval for work within a federal park. It also contends that these actions breach the U.S. Constitution’s property clause, which gives Congress authority over federal property.

Previously, the Trust had requested a construction pause in letters to the National Capital Planning Commission, the National Park Service, and the Commission of Fine Arts. While the administration has not formally responded to the lawsuit, officials maintain the project is legally compliant, Al Jazeera reported.

In October, White House Communications Director Steven Cheung dismissed the Trust as “run by a bunch of loser Democrats and liberal donors playing political games.” President Trump, with his real estate background, has strongly supported the ballroom project. Demolition of part of the east wing began in October, and the planned ballroom would seat nearly 1,000 guests, up from an earlier estimate of 650. The cost has risen from $200 million to $300 million, with the administration stating that private donors are funding the project.

If completed, the ballroom would be the most significant physical change to the White House during Trump’s presidency, substantially expanding beyond the current 55,000-square-foot footprint. Critics argue the expansion would overshadow the east and west wings, whose dimensions have largely remained unchanged since the early 19th century.