While the cities of Insul are in most senses city-states, due to the history of how they took up these responsibilities, they are seen and treated differently than what most players would expect of city-states.
In the mind of the citizenry, there isn’t really a distinction between the ruling city and the area they control and protect. Contriare the city, built up over the dividing river with its half timbered buildings, and the hundreds of square miles of rolling farmlands and woods beyond that are all seen as “Contriare”. Anyone that lives within this area and is part of the citizenry are called “Contriarans”. The towns beyond the city proper/city center are seen almost as a suburb of the city.
Town names are basically “town name under the protection of city”, commonly called just “town-under-city” or very casually “town city” like it has a last name. Additionally, a town would orient its location based on where it is in relation to the city proper first and foremost, rather than its surrounding towns, or to another city. So someone would say “I’m from Brookside-under-Contriare; it’s 50 miles southeast of the city proper.” Of course, if one’s already established their city of origin, it would be dropped “I’m a Contriaran from Brookside, 50 miles southeast of the city center.” If you don’t mention a city at all, it’s more or less immediately assumed you’re from the Between (for better or worse).
Regarding laws, each city is its own country in this regard, with its own set of laws that only apply within their own borders, though there is no restriction of travel, only what the city protects (and rules) and what it doesn’t. This doesn’t mean that there aren’t commonly agreed upon intercity laws: many of these have been pushed and advocated by the Merchant’s Council, and really focus on protecting capital. The cities also have things like unofficial extradition agreements and the like, but many of these sorts of things are case-by-case dealings.