<ins>Personal silly headcanon (not meant to be taken seriously):</ins>

Equestrian law states that all “Villain” class criminals be given punishments similar or equal to that of the crime they committed.

For instance, for the crime of stealing cutie marks, Starlight Glimmer had her cutie mark removed for one week.

For the crimes of assault and destroying historical artefacts, Stygian had his ancient collection of adult magazines burnt.

For the crimes of petrification of innocents and royalty, mass slavery, high treason, unlawful imprisonment, and assault… Yeah.