That’s illegal is term used by students in Wake Forest 2018. You say it when someone is saying or doing something that’s not “Tippropriate” or something that is considered sexual or profane.
Anytime someone does or says something that’s not tippropriate, you do the “Wakanda Forever” hand gesture and say “That’s illegal!” in a high pitch voice. This is a replacement for “that’s not tippropriate.”
It all started with a anonymous girl or boy, or animal (it’s 2018, you can’t assume anything). Every time a kid said something that was not tippropriate (William Huff), they would make an X with their hands and say “That’s illegal!” Little did they know that one day it will become a meme.
William: “SHIT! THAT’S A FUCKING WORM!”
Anonymous: “That’s illegal!!”