When former U.S. President Richard Nixon sat down for an interview with British journalist David Frost in 1977, Nixon asserted a broad interpretation of executive authority:
Frost:…Would you say that there are certain situations – and the Huston Plan was one of them – where the president can decide that it’s in the best interests of the nation, and do something illegal?
Nixon: Well, when the president does it, that means it is not illegal.
Frost: By definition.
Nixon: Exactly, exactly. If the president, for example, approves something because of the national security, or in this case because of a threat to internal peace and order of significant magnitude, then the president’s decision in that instance is one that enables those who carry it out, to carry it out without violating a law. Otherwise they’re in an impossible position.
You should note the context: If the president orders someone in the federal government to do something for a national security or domestic security reason, those individuals carrying out the president’s order “are not violating the law.”
Donald Trump and his shyster lawyers have taken Nixon’s assertion “[W]hen the president does it, that means it is not illegal,” and extended this to a blanket assertion of presidential immunity from (1) being subpoenaed in a criminal investigation, and (2) being indicted for criminal activity while president. It is a novel theory that the president is above the law, and a bold rejection of the bedrock foundational American principles that we are a nation of laws and that no man is above the law.