Dude, do the BAREST of research. Part (b) and because you will not read the link I will quote “Except as otherwise provided by the President and subject to such limitations and exceptions as the President may authorize and prescribe, it shall be unlawful for any citizen of the United States to depart from or enter, or attempt to depart from or enter, the United States unless he bears a valid United States passport.” Bolding is my own