20 U.S.C. § 1015d: In-State tuition rates for members of qualifying Federal service

In the case of a member of a qualifying Federal service whose domicile or permanent duty station is in a State that receives assistance under this chapter, such State shall not charge such member (or the spouse or dependent child of such member) tuition for attendance at a public institution of higher education in the State at a rate that is greater than the rate charged for residents of the State. If a member of a qualifying Federal service (or the spouse or dependent child of a member) pays tuition at a public institution of higher education in a State at a rate determined by subsection (a), the provisions of subsection (a) shall continue to apply to such member, spouse, or dependent while continuously enrolled at that institution, notwithstanding a subsequent change in the permanent duty station of the member to a location outside the State. This section shall take effect at each public institution of higher education in a State that receives assistance under this chapter for the first period of enrollment at such institution that begins after July 1, 2009 . a member of the armed forces (as defined in section 101 of title 10 ) who is on active duty for a period of more than 30 days (as defined in section 101 of title 10 ); a member of the Foreign Service (as defined in section 3903 of title 22 ) who is on active duty for a period of more than 30 days; or an officer or employee of an element of the intelligence community (as such term is defined in section 3003 of title 50 ) who serves in a position of employment in such element for a period of more than 30 days.