14 CFR 372.21: Solicitation.

Solicitation of charter participants through advertising by charter operators shall be restricted to the following:

(a) Radio and television stations operated by the U.S. Armed Forces;

(b) Newspapers, periodicals, or other printed media disseminated and distributed primarily among military personnel or civilian employees of the Department of Defense: Provided, however, That any printed advertisement of a charter operator shall include a statement explaining that eligibility for participation in such charters is limited to military servicemen who are stationed outside of the 48 contiguous States and the District of Columbia, and/or U.S. citizen civilian DOD employees who are stationed in a foreign country, or a U.S. territory or possession, where U.S. military personnel are stationed, and their respective immediate families.