Not knowing his background for sure,,, I would look at several aspects of his being there. Has he flown at you through the fence? Has he threatened your other chickens through the fence? If he was used for the purpose not being discussed blatantly, he would be doing all of these things and making it known he wants to be top dog. If he is just hanging around hoping for handouts then do what the others have suggested and wait until he is roosting and has been for at least an hour, sneak up on him and GENTLY pick him up by holding his wings in to his sides and hold him away from your body without making any sudden, jerky, moves that might alarm or scare him and put him in a kennel. Then you have the option of having him picked up, trying to find him a home, or making him his own little pen in your yard where he can't get out but is safe from predators and he can live out his life in comfort and won't be a threat to your little ones.