The Supreme Court has held: "Transmitting obscenity and child pornography, whether via the Internet or other means, is... illegal under federal law for both adults and juveniles." Reno v. ACLU, 521 U.S. 844, at 878 n. 44 (1998).

Federal law prohibits the distribution of obscenity through the facilities of interstate or foreign commerce.  More specifically, it is a crime to use the mail to send or receive obscene materials, to import obscenity, to ship or receive obscenity by a common carrier, or to transport obscene materials across state lines for sale or distribution, including by computer.  See 18 U.S.C. sections 1461, 1462, and 1465.  It is also illegal to broadcast obscene materials, or engage in the business of selling obscene materials that have traveled through interstate or foreign commerce.  See 18 U.S.C. sections 1464, 1466.  If on federal property, a military base, or on in Indian Country, it is a crime to sell or possess obscenity with the intent to sell.  See 18 U.S.C. section 1460.  (While even the mere possession of child pornography is a crime, private possession of obscenity is not, although the act of receiving obscenity could violate the statutes prohibiting use of the mails, carriers, or interactive computer services for the purpose of transporting such material.)

There are also federal laws making it a serious crime to distribute obscenity toward minors.  Federal law prohibits a person from using the mail, or any of the means of interstate commerce, including a computer, to knowingly transfer obscene materials to someone the person knows is under 16 years of age.  See 18 U.S.C. section 1470.  For example, it would be a crime to knowingly email an obscene picture to a 15 year-old.  Two other statutes for online child protection prohibit knowingly using an interactive computer service to display obscenity or child pornography in a manner that makes it available to a person under 18 (see 47 U.S.C. section 223(d) –Communications Decency Act of 1996, as amended by the PROTECT Act of 2003) and knowingly making a commercial communication via the Internet that includes obscenity and is available to any minor under age 17 (see 47 U.S.C. section 231 –Child Online Protection Act of 1998).   In addition, a new law also prohibits the use of Internet domain names with the intent to mislead a minor into viewing material that is harmful to minors, or mislead any person into viewing obscenity.  See 18 U.S.C. section 2252B.  For example, a pornographic Website cannot use a domain name suggestive of a cartoon character or children's television show with intent to mislead a minor into viewing harmful material.

The U.S. Supreme Court established the test that judges and juries use to determine whether material is obscene.  The test was developed in three major cases: Miller v. California, 413 U.S. 15, 24-25 (1973); Smith v. United States, 431 U.S. 291, 300-02, 309 (1977); and Pope v. Illinois, 481 U.S. 497, 500-01 (1987).  The resulting three-pronged test to adjudicate obscenity is as follows:

Whether the average person, applying contemporary adult community standards, would find that the work, taken as a whole, appeals to the prurient interest (i.e., an erotic, lascivious, abnormal, unhealthy, degrading, shameful, or morbid interest in nudity, sex, or excretion); and

Whether the average person, applying contemporary adult community standards, would find that the work depicts or describes, in a patently offensive way, sexual conduct (i.e., ultimate sexual acts, normal or perverted, actual or simulated, masturbation, excretory functions, lewd exhibition of the genitals, or sado-masochistic sexual abuse); and

Whether a reasonable person would find that the work, taken as a whole, lacks serious literary, artistic, political, or scientific value.

Any material meeting this definition may be found to violate the laws of the United States and anyone convicted of distributing such material may be prosecuted and punished by fines and a term of imprisonment.