49 USC 47133 - Restriction on use of revenues

(a) Prohibition.— 
Local taxes on aviation fuel (except taxes in effect on December 30, 1987) or the revenues generated by an airport that is the subject of Federal assistance may not be expended for any purpose other than the capital or operating costs of
(1) the airport;
(2) the local airport system; or
(3) any other local facility that is owned or operated by the person or entity that owns or operates the airport that is directly and substantially related to the air transportation of passengers or property.
(b) Exceptions.— 
Subsection (a) shall not apply if a provision enacted not later than September 2, 1982, in a law controlling financing by the airport owner or operator, or a covenant or assurance in a debt obligation issued not later than September 2, 1982, by the owner or operator, provides that the revenues, including local taxes on aviation fuel at public airports, from any of the facilities of the owner or operator, including the airport, be used to support not only the airport but also the general debt obligations or other facilities of the owner or operator.
(c) Rule of Construction.— 
Nothing in this section may be construed to prevent the use of a State tax on aviation fuel to support a State aviation program or the use of airport revenue on or off the airport for a noise mitigation purpose.