Our Legal Heritage: Gregory IX, the cat-killing pope who laid down the law.
Pope Gregory IX, the 178th pope of the Catholic Church from 1227 to 1241, is often remembered for issuing a Papal Bull declaring that cats bore Satan’s spirit, which subsequently led to huge numbers of cats being killed throughout Europe. The mass extermination of the continent’s felines is considered an indirect cause of the Bubonic plague spread by fleas on rats, which would otherwise have been hunted by the dead cats. Beyond that poor decision, Gregory was characterized as being quick to anger and having a “harsh personality”.
https://www.irishlegal.com/articles/our-legal-heritage-gregory-ix-the-cat-killing-pope-who-laid-down-the-law