And if it's a "long settled" legal principle, the Constitution still trumps however many courts have tried to make Jeffersons private correspondence Constitutional law. It's disingenuous and insulting to think she brought this up at random, totally ignorant of that classic Constitutional law debate. It's deliberately obtuse for a room full of lawyers to pretend that's not PRECISELY what she deliberately did, just so they can falsely accuse of her ignorance to justify mocking it. They are, to use a term they also know, begging the question, in this case "How can you be so stupid you don't know this?" when she very obviously does. It's not explicitly in the Constitution, which was carefully written by very smart lawyers. However many rulings have interpreted that language subsequently, those interpretations aren't an inherent part of the Constitution either, thus, like every other US law, they're subject to judicial review and reversal if found unconstitutional.