I'm not sure about Tennessee, but in Iowa you can. You have to either talk to your doctor, or a Judge, and the Judge can court committ him. Then he has no choice but to go.
Only with legal help and even then he may not come out of it as you would hope. The only one who can really help him, is himself. People barely get committed these days. They have to want the help and sometimes, only hard knocks can convince them. Best of luck to you.