and by 21st century, we mean 1964 (to non-USians, though, credit is given for "why should we care?")[1]:
Wikipaedia:
Quote
In the obscenity case of Jacobellis v. Ohio (1964), [U.S. Supreme Court Justice Potter] Stewart wrote in his short concurrence that "hard-core pornography" was hard to define, but that "I know it when I see it, and the motion picture involved in this case is not that."
1.
"Which is harder to find - a paranormal field agent, or someone competent who likes talking on the phone?"
"...You may return to your desk." "Thank you." -- Serena vs. Mr. Arthur,
"Paranormal Helpline", EGS:NP