
18 U.S. Code § 641 - Public money, property or records
Everything you do in government is govt property, that means your notes, your memos and your doodles. And it's illegal to take them from the government and use them for your own purposes. It's generally a minor crime, unless the information deals with something related to National Security.
Everything dealing with the POTUS is considered national security, until it is vetted as not National Security.