Except in emergencies, the medical treatment of incompetent patients also has to be based upon an informed consent between the physician and a legitimate legal representative (durable power of attorney). Consequently, the German 'Betreuungsrecht' advices persons to designate in advance such a proxy or surrogate. However, an additional court-decision is demanded, if a medical measure poses significant risks for the future health or the life of the incompetent patient. On the base of the available epidemiologic data we illustrate that neither our medical nor our legal system could realistically cope with the practical consequences of this legislation: The vast majority of our present decisions in such cases is not covered by a legally valid informed consent, which implies possible forensic consequences. This article provides relevant clinical and legal advice on how to protect the legitimate interests of all concerned within the present framework, which should urgently be revised.