I would add that the judicial branch has the Constitutional authority to obtain classified information and share it with jurors if needed for a trial, regardless of any statute.
The charges against Trump are simply absurd, which is why they have never been brought or even threatened against any other former President. And any President can simply pack up documents and say, "these are mine" while still in office.
The laws governing the handling of classified information (not the exact charges in this trial btw) are largely sanctified via executive orders of previous presidents. The current president is still subject to following the executive orders of previous presidents, up until he rescinds, and/or replaces them. A president is not legally able to just ignore them, which is why rescinding/replacing executive orders of previous presidents is usually one of the first actions a new president performs. Trump did not rescind any EO’s protecting classified while he was president, in fact, he proudly strengthened them, instead, and was therefore subject to them.