I'm writing a post about this morning's U.S. v. Williams decision, and I realized it would be good to lay out this brief guide — it might be helpful for future controversies, too.

I. Obscenity: The Supreme Court has held that the First Amendment does not protect the distribution of "obscenity," a narrow category that basically covers hard-core pornography. To be obscenity, a work must satisfy all three of the following elements, largely drawn from Miller v. California (1973):

1. "the [a] average person, [b] applying contemporary community standards, would find that the work, [c] taken as a whole, [d] appeals to the prurient interest,"

2. "the work depicts or describes, [a] in a patently offensive way [under [b] contemporary community standards, Smith v. U.S. (1977)], [c] sexual conduct specifically defined by the applicable state law," and

3. "the work, [a] taken as a whole, [b] lacks serious [c] literary, artistic, political, or scientific value[, [d] applying national standards and not just community standards."

Note also that, (4) mere private possession of obscenity can't be constitutionally outlawed, though distribution and even transportation for one's own private use may be. See Stanley v. Georgia (1969); U.S. v. Orito (1973).

II. Child Pornography: The Supreme Court has also held that the First Amendment does not protect the distribution or possession of "child pornography," which basically covers

1. "visual[] depict[ions]" of

2. actual children below the age of majority (and not just fictional pictures or pictures of adults who look like children)

3. "performing sexual acts or lewdly exhibiting their genitals."

See New York v. Ferber (1982); Ashcroft v. Free Speech Coalition (2002) a category that basically covers depictions of actual children in sexual contexts.

III. Distribution of Sexually Themed Material to Minors: The Court has held that the law may bar distribution to specific minors of sexually themed material, even if the material doesn't fall within the above exceptions. The test for such unprotected material is basically the Miller test (see item I above), with "of minors" or "for minors" added to each prong (e.g., "the work taken as a whole, lacks serious literary, artistic, political, or scientific value for minors"). Ginsberg v. New York (1968), a pre-Miller case, upheld a law that implemented the then-current obscenity test with "to minors" added at the end of each prong; most lower courts and commentators have assumed that Ginsberg plus Miller justify laws that implement the Miller-based test given above.

IV. Public Display of Sexually Themed Material, Where Minors and Offended Viewers Might See It Alongside Willing Viewers? It's not clear to what extent the government may bar this, at least assuming the material fits within the obscene-as-to-minors framework described in item III — the Court has struck down limits on Internet distribution of such material, but lower courts had upheld limits on non-Internet distribution and display, for instance through coin-operated newsracks. The Supreme Court has also strongly suggested that the display of such material -- including mere nudity and not just obscene-as-to-minors material -- on broadcast television is constitutionally unprotected.

V. Pornography More Generally: Sexually themed material that fits in none of the above categories is constitutionally protected, though the "erogenous zoning" cases allow greater regulations of — though generally not total bans on — bricks-and-mortar businesses, such as theaters and bookstores, that distribute pornographic material to walk-in customers.