“A decade ago, Congress decided it was time to address what a House report called ‘a very specific sexual fetish.’ There are people, it turns out, who take pleasure from watching videos of small animals being crushed. … So, in 1999, Congress made it a crime to sell ‘crush videos’ and almost all other depictions of unlawful cruelty to animals.” A Supreme Court case raises the question of whether the law violates the First Amendment.