There is a guard of blue-cloaks (City Guard) which are based in Highlake City but officially are the keepers of law for the island as a whole. Their head is the Banathus, Defender of Highlake (whom the main line PCs have met breifly), and his Speaker, Roi the Quickfingered (whom the main line PCs have met not quite so briefly).
Suspects are taken in by the guards, and for the majority of small crimes plead their case directly to the Defender or one he designates for that role (often the Speaker or a senior Guard).
Higher crimes (murder, acts against the state, religious matters) go before the Defender, the Keeper of the Open Waters, and one of the councilors (rotated from the other houses). The accused can petition through the councilor for their house (or effectively any noble of the house) to be heard before the complete Council in matters that involve high crimes or those of high status.
More Meta-OOC:
Or something along those lines. I think I had a draft document about law in Highlake, but one of the the plots didn't end up driving you guys into the legal system, so it didn't need to get finalized. Basically though there is no "jury of peers", and more of a class system in action where those of higher rank rule on those of lower rank.