You would be wrong about that. NO president can just keep whatever classified documents he wants.
You don't think doing so would piss off our allies? Especially when the president in question is a buddy of Vladimir Putin, who is not, shall we say, pro-American.
Yes, the Espionage Act was signed into law in 1917. So what? It's never been repealed.
The statute criminalizes a broad array of conduct related to the mishandling of sensitive government records connected to the "national defense," a term generally referring to military records that if disclosed could damage U.S. national security.
Over the years, the law has been used as a legal tool by the Justice Department to prosecute people ranging from suspected Soviet spies to famous whistleblowers like Daniel Ellsberg, who leaked the Pentagon Papers, and Edward Snowden, a former intelligence consultant who leaked classified National Security Agency records to reveal the existence of a domestic surveillance program.
I suggest you read the article. And I suspect you've been listening to the idiotic Christina Bobb, one of Trumpty's lawyers who is herself involved in this mess.