Thanks for writing. Marriage can happen in few DOCs and the BOP. It is, however, a long process for approval. Our advice is to have your inmate contact the chaplain and tell them what he wants to do. If they'll consider it, your inmate will get a list from the chaplain that you'll have to handle on the outside. If his sentence isn't too long, I would seriously consider waiting to have a proper wedding on the outside because of all you're going to have to go through to get approved.