This morning, declaring that "the White House is the People's House," a divided panel of the U.S. Court of Appeals for the D.C. Circuit upheld the district court injunction against the construction of the new White House ballroom. According to the court, "Whether or not a massive ballroom should be constructed is for Congress to decide and is not a matter for Executive self-help."
The 100-page majority opinion in National Trust for Historic Preservation v. National Park Service was written jointly by Judges Millett and Garcia. Judge Rao dissented.
The panel stayed its decision for fourteen days for the express purpose of allowing the Trump Administration to seek review from the Supreme Court, and I would expect such a filing in due course.