47 C.F.R. § 73.3999
Enforcement of 18 U.S.C. 1464 (restrictions on the transmission of obscene and indecent material)
(a) No licensee of a radio or television broadcast station shall broadcast any material which is obscene.
(b) No licensee of a radio or television broadcast station shall broadcast on any day between 6 a.m. and 10 p.m. any material which is indecent.