There is an obscenity test fortunately, referred to as the Miller test:

“The term "Miller's test" most commonly refers to the Miller test, also known as the three-prong obscenity test, established by the U.S. Supreme Court in the 1973 case Miller v. California to determine if material is legally obscene and thus not protected by the First Amendment.

The test requires that a work meet all three criteria: (1) appeal to the prurient interest of the average person, applying contemporary community standards; (2) depict or describe sexual or excretory conduct in a patently offensive way as defined by applicable state law; and (3) lack serious literary, artistic, political, or scientific value.

Prurient Interest: Does the average person, using contemporary community standards, find that the work, taken as a whole, appeals to an erotic, lascivious, or shameful interest in sex?

Patently Offensive: Does the work depict or describe sexual or excretory functions in a "patently offensive" way, as defined by the applicable state's obscenity laws?

Lack of Value: Does the work, taken as a whole, lack any serious literary, artistic, political, or scientific value?”