The law of we make things up so our guy is eligible. There is no current law that I know of that makes Cruz eligible. Rubio gets in as an anchor baby.
Marco Rubio is a de facto Citizen only due to a misinterpretation of the 14th amendment. Natural born Citizenship derives from Natural Law and requires birth in the country to Citizen parents (plural).
Marco Rubio is the son of two Cuban foreign nationals and is NOT a natural born Citizen.