Obama's documents are controlled by the National Archives. The documents are part of the Obama Presidential library.
Maybe that is Trump's defense. He took the documents for his Presidential library. But that is not plausible because Trump University was closed due to it being fraudulent. Even if Trump did have a Presidential library the national archives would still need to control those documents. Even if Trump did have a library neither he, his family members nor most of his followers could read anyway so there is no need for the library.