President Trump signed an executive order on Thursday designating the Oval Office a national monument, a move that bars future presidents from making major alterations to the room. Trump said the order would make it impossible for anyone to destroy or significantly change the historic space.

The executive order also extends to the Cabinet Room, according to a report from WMUR Channel 9. It directs the National Park Service to maintain the Oval Office “in a manner that protects its historic character, architectural integrity, and association with the Presidency,” the order states. The document notes existing protections for the White House but asserts that “nonetheless, the Oval Office merits specific recognition and protective management as a discrete historic structure of national significance.”

The action follows months of construction at the White House after Trump ordered the demolition of the entire East Wing, a project that faced legal challenges and was not approved by Congress, according to Yahoo News.

Trump told reporters Thursday that the designation would “make it impossible for anybody ever to destroy this incredible space.” He said the order was necessary to prevent the room from being “ripped down by stupid people, in order to build something in a slightly different shape.” He described the Oval Office as “a symbol, like the White House itself. It’s a symbol of our country and the greatness of our country.”

The order does not restrict a president’s authority to redecorate, select furnishings, or make ordinary operational and security modifications that do not substantially impair the monument’s historic structure or architectural character, according to the text of the order. Future presidents can still replace furniture and add personal touches, and the designation could be reversed by a subsequent administration, according to WMUR.

Construction has continued, with plans to convert the space into a new ballroom. Trump said Wednesday of the project, “It’s going to be the most beautiful ballroom in the world.”

Other changes Trump has made to the White House include a large gold plaque reading “Oval Office” outside the space, paving over the Rose Garden, and adding a new helicopter pad, according to Yahoo News.

The legal standing of the order is uncertain. Most executive orders can be overturned by a subsequent president, and a future administration could reverse Trump’s proclamation entirely, according to WMUR. Trump himself scaled back two national monuments in Utah in 2017, but revoking a national monument designation has not been tested in court, according to Yahoo News.

American presidents have the power to make some changes to the White House, but large projects require congressional permission, according to Yahoo News. The White House grounds are already designated as a National Historic Landmark, and Congress has carved out an exemption to the National Historic Preservation Act to allow presidents to make needed changes.

Greg Werkheiser, a lawyer with the firm Cultural Heritage Partners who specializes in historic preservation, called the order “hypocrisy,” noting Trump’s projects across Washington, including plans for a new triumphal arch that a federal judge has temporarily put on hold. Werkheiser said Trump is “absolutely taking an axe to the law that allows us to preserve other historic sites.” He said temporary alterations such as “furniture and decor is completely up to the president’s discretion,” adding, “As long as they’re not damaging the permanent art and architecture, they can generally do whatever they want.”

Trump claimed world leaders who visited in recent months complimented his decorative changes to the room, according to Yahoo News. He described the White House and Oval Office as “badly damaged” before his changes, citing broken windows, cracked walls, and broken stone.

The current Oval Office has existed since the early 1930s, after its conception by President Franklin D. Roosevelt.