22 CFR § 50.10
Certificate of nationality
November 19, 2020
(a) Any person who acquired the nationality of the United States at birth and who is involved in any judicial or administrative proceedings in a foreign state and needs to establish his U.S. nationality may apply for a certificate of nationality in the form prescribed by the Department.
(b) An applicant for a certificate of nationality must submit evidence of his nationality and documentary evidence establishing that he is involved in judicial or administrative proceedings in which proof of his U.S. nationality is required.