22 CFR 305.2 - Eligibility.
In order to be eligible for enrollment as a Volunteer, Applicants must meet mandatory citizenship and age requirements.
(a)Citizenship. The Applicant must be a citizen or national of the United States prior to entering on duty as a Trainee.
(b)Age. The Applicant must be at least 18 years old at the time of entry on duty as a Trainee.