Have them go through customs every time they leave their property to get groceries.
Get yourself a conscientious officer who makes sure he doesn't have enough hours in a day to fetch something he forgot on his first run.
Btw, tough luck with your utilities, I assume it's quite a lot of paperwork for international piping and electrical connections, especially if your utilities company is motivated not losing 100$ a month.
Only thing worse than citizenship is statelessness.
You think the government is fucking you over now? Wait till you're denied legal residency practically anywhere on earth and your very existence is considered a criminal trespass.