Suiyan
Wording is everything. Some evildoers are only too happy to slide a monkey wrench into the works using loopholes. One way, they have to do no harm and provide support... forever. Another way, they only have to do no harm, until they leave the city. A third option restricts all of that to only the timeframes that they are in the city... forever. Get your wording straight or it could be your undoing.