How can you stop someone from leaving the country?

Well it depends on why you do not want them to leave the country. The easiest way is to look into your state and federal laws in order to have their passport revoked. But unfortunately if they are determined to leave all they have to do is to cross the Canadian boarder. Since there really are no checks there it can make it very easy for a person to leave the country as well as return with just having to show their state ID. Every other form to keep them in country besides having them placed in prison is well lets just say can put you in jail