§ 435.407 Types of acceptable documentary evidence of citizenship.
(a) Stand-alone evidence of citizenship. The following must be accepted as sufficient documentary evidence of citizenship:

(1) A U.S. passport, including a U.S. Passport Card issued by the Department of State, without regard to any expiration date as long as such passport or Card was issued without limitation.

(2) A Certificate of Naturalization.

(3) A Certificate of U.S. Citizenship.