First: The news of the day, then Senator Marco Rubio’s father was not a naturalized citizen when Marco was born in May 1971 per National Archives data. His father applied for naturalization in Sep 1975. Marco Rubio not constitutionally eligible to run for President or VP. A natural born Citizen of the United States is one born in the United States to two U.S. Citizens who were Citizens of the United States either by birth or naturalization at the time of the birth of the child. A natural born Citizen of the United States is a child born with sole allegiance to the United States, a person born without Citizenship in any other country other than the USA at the time of their birth. The works in  Vattel’s Law of Nations , was used by the first and second continental congress to form our constitution and declaration of independance, It explains the difference between naturalized and natural born Citizen !