In this section the following words have the meanings indicated. “Eligible service member” means: An active service member; and A veteran who has received an other than dishonorable discharge or a certificate of satisfactory completion of service. “Eligible spouse” means the spouse of an eligible service member. Subject to subsection (c) of this section, a public institution of higher education shall grant priority registration for courses to an eligible service member or eligible spouse. The priority registration requirement under subsection (b) of this section: Applies only within 15 years after the eligible service member who would receive or whose eligible spouse would receive priority registration was last on active duty; and Does not apply after an eligible service member’s or eligible spouse’s fourth academic year. Each public institution of higher education shall adopt policies necessary to implement this section.