U.S. District Judge Richard Leon ordered a halt to construction of President Donald Trump’s planned White House ballroom until Congress authorizes its completion, issuing a preliminary injunction in favor of the National Trust for Historic Preservation.

The judge said the group is likely to succeed in its lawsuit and emphasized that the president is a steward of the White House, not its owner.

Enforcement of the order is delayed for 14 days to allow for an expected appeal, and limited construction may continue for security reasons.

The ballroom project, estimated to cost at least $300 million, has drawn significant public opposition and procedural challenges, NPR has reported.

The ruling comes ahead of a planned vote by the National Capital Planning Commission on the project.