(a) A person employed in the service of a vessel is considered to be acting under the authority of a credential or endorsement when the holding of such credential or endorsement is:

(1) Required by law or regulation; or

(2) Required by an employer as a condition for employment.

(b) A person is considered to be acting under the authority of the credential or endorsement while engaged in official matters regarding the credential or endorsement. This includes, but is not limited to, such acts as applying for renewal, taking examinations for raises of grade, requesting duplicate or replacement credentials, or when appearing at a hearing under this part.

(c) A person does not cease to act under the authority of a credential or endorsement while on authorized or unauthorized shore leave from the vessel.