Following the Watergate scandal, Congress enacted two laws aimed at preserving presidential records. The Presidential Recordings and Materials Preservation Act of 1974 applied specifically to Richard Nixon, blocking the destruction of his White House tapes. Four years later came the Presidential Records Act (PRA), which applied to future administrations. Under that law, "the United States shall reserve and retain complete ownership, possession, and control of Presidential records," which belong with the National Archives and Records Administration (NARA).
According to Donald Trump, that principle is essentially meaningless, because a president can arbitrarily classify any records as "personal" rather than "presidential." In fact, the former president says, no explicit designation is necessary: When he took thousands of documents with him upon leaving the White House in January 2021, that very act transformed them into "personal" records that are not subject to the PRA.
