The KGB, according to Thomas Rid in Active Measures, operated under the guiding principle that the governments of free societies pay a heavy penalty for lying. After all, they govern by consent and falsehoods are a well-established justification for revocation of consent. The governments of authoritarian societies, on the other hand, face zero penalties from lies because they govern by force. Truth is actually more expensive than lies for authoritarian governments because it offers the possibility for accountability.
Courts are authoritarian by definition. Judges decide what goes. There is a hierarchy of judicial power and the ground rules of legal systems require those judges to adhere to codes and standards by various degree, depending on the strength of the judiciary. Potter Stewart ducked responsibility with his "I know it when I see it" line, and regretted it towards the end of his life. It was a standard that took two other supreme court cases to iron out:
Whether "the average person, applying contemporary community standards", would find that the work, taken as a whole, appeals to the prurient interest,
Whether the work depicts or describes, in a patently offensive way, sexual conduct or excretory functions specifically defined by applicable state law,
Whether the work, taken as a whole, lacks serious literary, artistic, political, or scientific value.
Wittgenstein would likely have approved of the "average person" test and condemned the "lacks serious value" test. But he also would have likely argued that pornography is, by definition, a culturally fluid thing. Potter Stewart? Wrote the dissent in Griswold v. Connecticut:
"I get nowhere in this case by talk about a constitutional 'right of privacy' as an emanation from one or more constitutional provisions. I like my privacy as well as the next one, but I am nevertheless compelled to admit that government has a right to invade it unless prohibited by some specific constitutional provision."
"I know it when I see it" is the verbiage you use when you want to maintain absolute power in the judge rather than the law. It's exactly where the Republicans want to go, because the Republicans have been unabashedly authoritarian since Sarah Palin.