However, in the United States, the 1973 ruling of the Supreme Court of the United States in Miller v. California established a three-tiered test to determine what was obscene - and thus not protected, versus what was merely erotic and thus protected by the First Amendment.
Delivering the opinion of the court, Chief Justice Warren Burger wrote,
The basic guidelines for the trier of fact must be: (a) whether 'the average person, applying contemporary community standards would find that the work, taken as a whole, appeals to the prurient interest, (b) whether the work depicts or describes, in a patently offensive way, sexual conduct specifically defined by the applicable state law; and (c) whether the work, taken as a whole, lacks serious literary, artistic, political, or scientific value.[2]
http://en.wikipedia.org/wiki/Obscenity
There is a three tier test to DETERMINE if an image is obscene, a picture of a woman getting milk poured on her would not be found obscene by most people, however blasting it out of a girls ass, could be.
Try reading you fucking noob.
http://en.wikipedia.org/wiki/Miller_test