A federal judge on Tuesday temporarily blocked President Trump's sprawling plans to build a massive ballroom where the East Wing of the White House once stood.Why it matters: U.S. District Judge Richard Leon said Trump is the "steward," not the "owner" of the White House, and that the project "must stop until Congress authorizes its completion."The big picture: The demolition of the 120-plus years of East Wing history and the $400 million expansion project have roiled Washington as the president leaves his gilded mark on an increasingly Trump-ified district.Driving the news: Leon granted the National Trust for Historic Preservation's request for a preliminary injunction, halting the administration's fast-tracked plans.The trust has argued that the White House needs congressional approval for the extensive renovations and argued in filing earlier this month that "the President is a temporary tenant of the White House—its steward, not its landlord," a notion that Leon echoed in his 35-page opinion.Catch up quick: The Commission on Fine Arts, which is packed with Trump loyalists, gave the ballroom design a swift thumbs up in February.The National Capital Planning Commission (NCPC), also stacked with friendly faces, is set to vote in April.Friction point: The National Trust for Historic Preservation sued the president and other federal agencies in December, arguing that the demolition violated the Constitution and asked the judge to block construction until a required review process, including a public comment period, is completed."No president is legally allowed to tear down portions of the White House without any review whatsoever—not President Trump, not President Biden, and not anyone else," the complaint said.In February, Leon said he could not "address the merits of the novel and weighty issues raised" without the Trust amending its argument. It did so, requesting a new injunction this month. The government argues that ceasing construction would endanger national security. In March, the NCPC released over 9,000 pages of public comments criticizing the ballroom project.One woman implored, "NO GAUDY FAKE GOLD STUFF ALL OVER THE PLACE," and Republican Rep. Michael Turner (R-Ohio) called images of the bulldozed White House grounds "deeply disturbing."What we're watching: Despite the legal challenges and public outcry, the White House aims to have the project done "long before the end of President Trump's term."Go deeper: East Wing expansion plans revealed as Trump team pushes for fast-track approval