Yes, because one's life is one's own property. It is immaterial whether one believe's this is signalling societie's 'approval' of suicide, as so long as I do not violate another person's life, liberty or property, what I do with my own life is my own business, regardless of societie's 'approval'. Does one's suicide upset friends and family? Undoubtably. So does one's slow suicide by drinking or drug use. Should those things be illegal? As a libertarian, I say no. (There is a separate issue of what to do in the case of leaving behind unfinished business, whether it's offspring, or an unpaid debt. But just as there are legal ways to handle this when it happens in cases of sudden accidental death, there should be similar legal ways to deal with it in cases of suicide).
Anyways, the title of this thread is a misnomer. How do you legally punish someone who has committed suicide? The real question is, should attempted suicide be legal? I still say yes. Your life is your own. That doesn't mean that I won't try to talk the person out of it, if I feel their reason is out of depression. It is that I cannot force them to substitute my ( or societie's) judgement over their own for what should essentially be their decision.
If it isn't for reasons of terminal illness, and is an out-and-out case of depression, is suicide a sign of mental illness? Perhaps. But, just as in the case of alcoholism and substance abuse (including prescription drugs), the time for the law to step in with cases of mental illness is when the person has violated, or threatened to violate, another person's life liberty or property. Just as there are organisations like AA to deal with alcoholics, there are several organisations to help people deal with depression that some feel might lead to suicide.
Inquiry: if it were to be illegal, what should be the punishment for attempted suicide? A fine? :scratch: That should take the weight off the would-be's shoulders. Incarceration? :disagree: What a great idea, putting a guy/gal who doesn't feel life is worth living intogether with murderers, rapists, arsonists, fraud-schemers, etc. My guess is that if a person has attempted suicide, but failed, there are those who feel the person should be committed to a psychiatric institution, and forced to undergo therapy. Sorry, but incarceration is still incarceration. The end does not justify the means.
I'm not trying to treat the subject lightly. Several years ago, an Uncle of mine committed suicide. But that was his decision, just as some acquaintances decision to commit slow drawn-out suicide with drink or drugs was theirs. Society should be built upon choice, even if the choices might be most upsetting for loved ones.