Hmm... Thinking has occurred, and I believe perhaps that banning baddies from your township is almost enough. Almost. Particularly when you come around to cooperation between towns. You have an incident, ban the offender, and spread it around so that the guy is basically hunted down when spotted within your kingdom or empire. From there, you stick his name up on your town blacklist, other people can refer to that and end up denying him access as well. So long as the habits get started, people may end up fearing expulsion from a portion of the server and simply not commit the crime.
On the other hand, it's pretty easy for those jaded types to simply disregard the consequences of such actions and avoid retribution. He may set up LWCs in the wilderness or join a township that doesn't care about criminals (or even encourages them to join). And from there? He could become a constant nuisance or do the same thing elsewhere.
Still, some form of authority should come with being a town leader. I'd like to posit a server rule stating that a citizen has to comply with a town leader's decision to punish you for something against the town's rules, so long as the punishments are clearly stated before the incident begins and aren't disputed as unreasonable. Fines, compensation, and temporary imprisonment come to the table. This is off the top of my head, but it seems like it would cut back on the petitions the staff would receive for commenting on town politics while providing a solid form of law in a town, instead of "hey guys, I'd really like you to follow this rule here".
Under this rule, I'd imagine town regulations looking a bit like this:
1. Basements may be 10 blocks deep. There is a fine of 3 gold or 30c for every block dug out beyond the 10-block limit.
2. Thievery is not tolerated. Anyone found stealing from another citizen will repay all stolen materials or their value in coin, and an additional 50c in coin or goods. Afterwards, the offender is temporarily removed from the town region and sentenced to an hour in the dungeon. Accusations may be discussed prior to punishment, potentially resulting in minimizing the punishment to willing reimbursement of the victim.
It would take some hammering out, but I feel potential here. Perhaps limit such authority to towns of a Kingdom or Capital cities...