As discussed earlier, the medical profession has long argued that suicide is most likely the outcome of a psychiatric illness. This makes rational suicide a contradiction in terms. If a person wants to die - regardless of the context - then QED they were not thinking rationally. Of course, Exit disagrees.
Luckily, ‘the law’ (vis a vis medicine) has never gone down the path of automatically equating suicide with mental illness. Rather, when adjudicating on suicide, the courts often find no indication of mental illness. To this end, the law does not see suicide as the outcome of mental illness. Indeed, some suicide notes have even been upheld as wills. Two birds with one stone as they say.