10 U.S.C. § 8470a — Permanent professors: retirement for years of service; authority for deferral

(a) Retirement for Years of Service.
(1) Except as (b) allows, a Navy or Marine Corps officer^* serving as a permanent professor at the Naval Academy in the grade^* of commander or lieutenant colonel, who is not on a list recommended for promotion to captain or colonel, must retire — if not already retired — on the first day of the month after completing 28 years of active commissioned service.
(2) Except as (b) allows, a permanent professor holding the grade of captain or colonel who is not on a list recommended for promotion to rear admiral (lower half) or brigadier general must retire — if not already retired — on the first day of the month after completing 30 years of active commissioned service.

(b) Continuation on Active Duty^*.
(1) An officer subject to retirement under (a) may have that retirement deferred and be kept on active duty by the Secretary of the Navy.
(2) Subject to section 1252 of this title, the Secretary of the Navy decides how long that continuation lasts.

(c) Eligibility for Promotion. A commander or lieutenant colonel kept on active duty as a permanent professor under (b) remains eligible for consideration for promotion to captain or colonel.

(d) Retired Grade and Retired Pay^*. Each officer retired under this section: (1) is retired in the grade set under section 1370 of this title, unless entitled to a higher grade; and (2) is entitled to retired pay computed under section 8333 of this title.