I would say that since no one really knows what the laws in Eorzea really are, some common sense applies. Things like treason, theft, murder, and any type of brutality would obviously incur some jail time (or even time in the arena for Ul'dah), however I don't think a bar brawl will end with you getting arrested by Wood Wailers. I also don't expect anyone to RP that they spent three weeks in jail if they don't want to.
To add to that, there are also some cultural differences to take in. For instance, Ishgard probably has some laws surrounding their military discipline and religious zeal.
To add to that, there are also some cultural differences to take in. For instance, Ishgard probably has some laws surrounding their military discipline and religious zeal.