14 CFR §1241.20

1. (a)This section sets forth those persons who, by the provisions of the TREAT Astronauts Act, are eligible to participate in this program. A determination by the Administrator or designee that a person is eligible does not automatically entitle such a person to medical monitoring, diagnosis, and treatment under the TREAT Astronauts Act.
2. (b)Only eligible individuals defined in § 1241.15 are entitled to medical monitoring, diagnosis, and treatment under this part.
3. (c)Participation in this program is strictly voluntary. NASA may not require an eligible individual to participate in this program.