Trump admin lawyers filed in court that the preservation society seeking to review his plans and maybe curb them has no standing and that the completion of the ballroom is essential for "national security." When asked to explain that they refused, said it's classified and offered to share it with a judge in a proper secure environment.
Yep the ballroom is necessary for national security. Even got a member of the secret service to swear in writing that it's essential for security.
I can somewhat get an argument for the security of Trump and people in the White House, there's a gaping hole there now that could be used to access the White House in theory from underneath. And there is the so called underground bunker system that the East Wing had below.
But the argument the Trump admin is making is the security of the entire country is in danger if it's not finished which is preposterous