The day before the Kaede character is due to return, Tetsuma returns from one of their trips into town and says, "So I think I have a decent-ish idea of local law. Somewhat. The clone bound for Cloudsheer still isn't there, but the other two have found some things, including a small legal library - apparently one of the neighboring islands is big on self-advocacy. I also bugged the magistrate's assistant in Laelora a bit."
"Apparently, jurisdiction is a complicated mess, since the ley makes maintaining a multiple-island empire really, really difficult, and most islands aren't in a jurisdiction. So if you're a citizen of a nation, you can drag someone into their civil courts no matter where the offence occurred. Some nations allow anyone to bring a case to them. Theoretically, you could judge this, since you're a prince and all, and the nations around here would acknowledge the outcome, as long as at least one of the parties asks you to sit in judgement. So since Reim is accusing Lingormr of stealing the jewel, he could pick a nation - probably Bajilda, this area's in their sphere - present his case there, and they'd rule. Though if Lingormr chooses to ignore them, there's not much they can do since he's a local lord, short of outright war."
"As far as inheritance goes, most places it's similar to my world - your land and belongings either go to a single heir or are occasionally split up among your children. Most places allow verbal wills, for people who're childless or who've disowned their kids. Bajilda has wills more like your world. Here, and in neighboring islands, if a verbal will is given before witnesses by a childless person, and then a child is born, the verbal will is considered obsolete, and inheritance defaults to the child unless the will's given again. Wills can also be retracted or changed. So legally it matters if Reim was born before or after his mom promised Lingormr the jewel, and if she ever changed her mind. Though apparently it's really atypical to leave things to multiple people - verbal wills are usually just stating a single heir."