Regnans in Excelsis

Regnans in excelsis is an old saying that means "reigning on high." Essentially, it's a fancy way of saying that someone is in charge or has power over something. In history, this saying was commonly used in the context of the Catholic Church.

Back in the day, the pope (the leader of the Catholic Church) had a lot of power over things that happened in certain countries. For example, if the king of England did something that the pope didn't like, the pope could excommunicate him - which basically meant saying he was not allowed to be a part of the church anymore. This was a big deal because religion was really important to people in those days.

Regnans in excelsis was used in a document called a "papal bull" that the pope sent to England's queen, Elizabeth I, in 1570. In the bull, the pope basically said that Elizabeth wasn't doing a good enough job of being Catholic (the religion that he led) and that she was basically a bad leader. He also said that nobody was allowed to support her anymore and that she was no longer allowed to be queen.

This was a pretty big deal, because it meant that Catholics in England were no longer allowed to follow their queen, and it made things really difficult for Elizabeth (who was actually a Protestant, not a Catholic). It also helped to fuel tensions between Catholics and Protestants, which would continue to be a big deal in England for many years.