1)  The first amendment does not exclude from its reach depictions of animal cruelty.  Though a few forms of speech -- obscenity, incitement to imminent violence, defamation -- are entirely unprotected by the first amendment, the Court refused to expand that category to encompass animal cruelty.  The Court rejected as unprecedented and contrary to the constitution the government's invitation to adopt a balancing test for defining categories of unprotected speech in language that deserves repeating:

"The Government thus proposes that a claim of categorical exclusion should be considered under a simple balancing test: "Whether a given category of speech enjoys First Amendment protection dependsupon a categorical balancing of the value of the speech against its societal costs." Brief for United States 8; see also id., at 12.

As a free-floating test for First Amendment coverage,that sentence is startling and dangerous. The First Amendment's guarantee of free speech does not extend only to categories of speech that survive an ad hoc balancing of relative social costs and benefits. The First Amendment itself reflects a judgment by the American people that the benefits of its restrictions on the Government outweigh the costs. Our Constitution forecloses any attempt to revise that judgment simply on the basis that some speech is not worth it. The Constitution is not a document "prescribing limits, and declaring that those limits may be passed at pleasure." Marbury v. Madison, 1 Cranch 137, 178 (1803)."

2.  Because the statute regulated within the reach of the first amendment, the Court turned to whether the statute was overbroad, and, because it punished any depiction of injury or killing, whether or not cruel, of animals illegal in any state in the country, found that it was substantially overbroad and therefore unconstitutional on its face.  For that reason, the Court did not have to decide whether a more narrowly drawn statute punishing only crush videos or extreme animal cruelty would pass constitutional muster.

[W]e have a duty to interpret §48 so as to avoid serious constitutional concerns, and §48 may reasonably be construed not to reach almost all, if not all, of the depictions that the Court finds constitutionally protected. Thus, §48 does not appear to have a large number of unconstitutional applications. Invalidation for overbreadth is appropriate only if the challenged statute suffers from substantial overbreadth--judged not just in absolute terms, but in relation to the statute's "plainly legitimate sweep." Williams, 553 U. S., at 292.

Another clause exempts depictions with "serious religious, political, scientific, educational, journalistic, historical, or artistic value."

An interesting aside from Roberts's opinion:

Even cockfighting, long considered immoral in much of America, see Barnes v. Glen Theatre, Inc., 501 U. S. 560, 575 (1991) (SCALIA, J., concurring in judgment), is legal in Puerto Rico, see 15 Laws P. R. Ann. §301 (Supp. 2008); Posadas de Puerto Rico Associates v. Tourism Co. of P. R., 478 U. S. 328, 342 (1986), and was legal in Louisiana until 2008, see La. Stat. Ann. §14:102.23 (West) (effec- tive Aug. 15, 2008). An otherwise-lawful image of any of these practices, if sold or possessed for commercial gain within a State that happens to forbid the practice, falls within the prohibition of §48(a).

In holding that §48 violates the overbreadth rule, the Court declines to decide whether, as the Government maintains, §48 is constitutional as applied to two broad categories of depictions that exist in the real world: crush videos and depictions of deadly animal fights. See ante, at 10, 19. Instead, the Court tacitly assumes for the sake of argument that §48 is valid as applied to these depictions, but the Court concludes that §48 reaches too much protected speech to survive.

If I ever catch anybody doing this to an animal (for profit or otherwise) I'm going to beat every cell that makes them want to do it out of them. Then we can all express ourselves freely in this highly advanced society.