22 CFR 50.11: Certificate of identity for travel to the United States to apply for admission.

(a) A person applying abroad for a certificate of identity under section 360(b) of the Immigration and Nationality Act shall complete the application form prescribed by the Department and submit evidence to support his claim to U.S. nationality.

(b) When a diplomatic or consular officer denies an application for a certificate of identity under this section, the applicant may submit a written appeal to the Secretary through the U.S. embassy or consulate where the individual applied for the certificate of identity, stating the pertinent facts, the grounds upon which U.S. nationality is claimed, and his or her reasons for considering that the denial was not justified.