If he declassified the documents, he’s never said so in any official capacity, including telling the DoJ or the court. Whether he did or not remains to be seen.
Whatever he did with them, it doesn’t mean he can defy a grand jury subpoena. That’s why he got raided. It wasn’t illegal and it wasn’t wrong. Trump brought it on himself by lying.
Who is the “investigator” and when did they say it?
A crook like Trump surely would abuse his office to make his own legal problems go away. Yet another reason not to vote for him.