The only catch, is that - since Obama was in office - the NARA has established how the documents are to be marked DECLASSIFIED.
It is a nit that the DoJ/FBI has chosen to pick. The DoJ/FBI moves, are designed to shed a negative light on Trump, when the issue is a small matter: the markings.
Before Obama, this matter of how and when declassified papers whould be marked . . . was even a smaller matter; but, Obama took steps to refine the policies about the steps to take when classifying and declassifying.
Because, there were apparently many hundreds of thousands of papers that were in the queue to be declassified - but the process had bogged down.
The NARA is supposed to spell out steps for the President to take, but the NARA has let the matter slide (except for the DECLASSIFIED markings), because the general feeling, mood, and thought about, what a President should do, has been left to the President.
The case is meant to look bad for Trump, but the case boils down to:
Shall a former President follow Federal Regulations to the letter, regarding his handling of the papers of his administration and of the United States, which papers fall under either of CLASSIFIED or DECLASSIFIED status.
The left, of course, wants the courts to decide what falls under those two categories, but tradition, and the law still supports the President, former or present, choosing what falls under those two categories . . . except now, if DECLASSFIED, there are some established steps for marking the documents, more clearly so.