Indeed, the right of an American to enter America is "absolute, unconditional, and irrevocable". They can arrest you immediately, or quarantine you for whateve

Indeed, the right of an American to enter America is "absolute, unconditional, and irrevocable". They can arrest you immediately, or quarantine you for whatever disease, but they can never turn you away if you insist on coming in. In theory. In practice, if the government doesn't want to believe you're a citizen then your right to enter isn't quite so strong.