This is yet another example in a long line of examples of why this supreme court is awful. This is a very clear first amendment violation, and the brief is supported by two well-known first-amendment champions, and yet the supreme court decided to not hear the case. According to the 6th district court of appeals, you now have to explicitly state that a piece is satire before you can write anything satirical, or else potentially face charges.
It starts out as ridiculous as you'd expect from the Onion, but it's a serious legal filing as a amicus curiae ("friend of the court" - a person or group who's not a party to the case but is interested and wants to give advice).