Have you given thought to how international law might shape your world? Even having notes on which nations subscribe to a body of international law standards can be a fun way to add depth to the political landscape.

Legal systems can be interesting (no really!) Americans and Britons are used to a common law, where legal precedents form the basis for future rulings, but there are other forms as well - the Roman system of civil law, and the Muslim system of Sharia law also exist.

In my setting, a fallen empire’s legal system formed the basis for a loose international treaty for the kingdoms that arose in its place - thus, the Pandect, a series of codes and standards to which today’s kingdoms and republics all either flout, follow, or attempt to follow in various ways.

https://kanka.io/en/campaign/7004/notes/4851

Have you ever tried making your own legal code? You are hereby sentenced to share.