His Lawyers are saying that if they reveal that Trump didn’t declassify any documents, that could subject him to legal action for stealing and holding highly classified information. Which he did. And if Trump claims he did declassify documents, then he’ll have to prove that in court, and also be subject to possible charges over failure to follow the law regarding declassification. Plus, there’s the whole perjury issue—and the issue of Trump obstructing an investigation—that comes with lying about the whole thing.

Source: Whoops! Trump’s ‘Special Master’ Is Holding Him Accountable | Crooks and Liars