Held: Under our constitutional structure of separated powers, the nature of Presidential power entitles a former President to absolute immunity from criminal prosecution for actions within his conclusive and preclusive constitutional authority. And he is entitled to at least presumptive immunity from prosecution for all his official acts. There is no immunity for unofficial acts.
The President enjoys no immunity for his unofficial acts, and not everything the President does is official. The President is not above the law.
https://www.supremecourt.gov/opinions/23pdf/23-939_e2pg.pdf