I can’t remember the quote.......... “all that is not mandatory is banned” ...... or something to that effect.
I read it in “The Once and Future King” by IIRC T.E.White.
“Whatever is not prohibited is mandatory”.
In the ant kingdom King Arthur as a boy, saw the sign, when Merlin was teaching him by having him become various creatures.
T. H. White, “The Once and Future King.”
“Everything not forbidden is compulsory.” It was a sign above the entrance to an ant colony.