> You're skirting around the key basis of almost all systems of justice: you do have a right to autonomy as long as you don't violate other's equal right to the same. This is basically the Non Aggression Principle, and it has the effect of maximising personal autonomy.
Many modern legal systems thoroughly limit the autonomy of individuals with regard to suicide, either by directly criminalizing it, by criminalizing any assistance others might provide a suicidal person in achieving that aim (in some systems even criminalizing merely failing to prevent a suicidal person from succeeding), or by authorizing other people to use force to prevent an individual from achieving that aim.
Suicide is an extreme case, but it's an extreme case in which usually no one's autonomy or body except the suicidal person's is involved. If an absolute right to our own bodies where it does not interfere with the rights of others is a key principle of our legal systems, then we should expect our legal systems to place no limitations on it, beyond at most restrictions aimed at preventing others from coercing an individual to commit "suicide", but this is not what we see in almost any modern legal system (if anyone has an example of one which does fit that expectation, I'd be curious to hear it).