(a) It is unlawful for a citizen of the United States, unless excepted under 22 CFR 53.2, to enter or depart, or attempt to enter or depart, the United States, without a valid U.S. passport.
(b) For purposes of this part ``United States'' means ``United States'' as defined in section 215(c) of the Immigration and Nationality Act of 1952, as amended (8 U.S.C. 1185(c)).