Should a person who does not wish to live be forcibly prevented from committing suicide?

John doesn't like living. He finds no joy in life, and only lives because it would upset other people if he ended his life. He has tried counseling and medication, but he simply has no desire to continue to live. He makes no real contribution to society, nor does he wish to be a part of society. If John wants to die, he can, but the state will attempt to stop him at every turn, even to the point of incarceration. Is there a point when the law (and other people) should simply respect his wishes and allow him to end his life -- or perhaps even assist him in doing so?