This is a law about informed consent.
I won't translate it verbatim, but it says more or less what one might have guessed it would say: i.e. that doctors need informed consent from the patient; or must consult with the patient's proches, except in emergency.
The noun proches literally means the patient's "nears", which is a word like "kin" except that in this case it can mean family, or it can mean anyone else who the patient has designated as being the person in whom they have "confidence", which could even include e.g. the person's GP -- effecting such a designation doesn't need a notary (but may require lucidity): they can give you a form at the hospital.
The above is a law, i.e. one of the laws: there are others -- see e.g. France passes new end-of-life legislation to alleviate suffering dated 2015, which also mentions a 2005 law (named la loi Leonetti):
France legalised “passive euthanasia” in 2005, where treatment, needed to maintain life is withheld or withdrawn
I don't know of English transcriptions of these laws, but Google Translate provides an IMO mostly-understandable translation of such web pages. Alternatively it's my experience that in a French hospital you may find that the doctor (or at least, that one of the doctors or nurses) can talk in English.
See also e.g. http://www.chu-nice.fr/patient-visiteur/vous-informer/droits-du-patient/1963-consentement-du-patient-et-le-refus-de-soins (which is a random hospital explaining the "informed consent" and in a more lay language).
Note that doctors may recommend or argue in favour of a course of treatment, and not accept a first refusal, and are for example expected to inform you of the likely consequences of withdrawing from treatment (that's part of your being "informed" so that you can give or refuse informed consent), which I suppose could seem like a refusal on their part; but so far as I know (i.e. in theory, based on the information such as I've referenced here) the patient (or their next of kin or their "designated trusted person") should (must in principle) be consulted and may say no.
As an aside, some people's personal experience has been that sometimes it seems as if some French doctors are more willing to divulge apparently bad news (e.g. a fatal or terminal prognosis) to the patient's kin than to the patient themselves.
Reading the small print of Article 36 again isn't entirely clear:
- Clearly the patient has a right to refuse treatment.
- Equally clearly in case of emergency the doctor doesn't need permission before treating.
- What's less clear is whether the the proches are allowed to refuse consent if the patient is incapable: what it actually says is that the doctor must "consult" with the kin.
So actually the other http://www.chu-nice.fr/patient-visiteur/vous-informer/droits-du-patient/1963-consentement-du-patient-et-le-refus-de-soins text has this paragraph which gives additional detail:
1- Patient hors d’état d’exprimer son refus :
Lorsque le patient est hors d’état d’exprimer sa volonté, que ce soit du fait d’un état passager limitant ou abolissant tout discernement (toxicomanie…) ou d’un état comateux ou d’inconscience passagère, le médecin doit prévenir la personne de confiance s’il en existe une, ou à défaut un proche.
Face au refus de soins exprimé, au nom du patient, par la personne de confiance, ou un proche, ou par le patient dans ses directives anticipées, le médecin va devoir mettre en place une procédure dite collégiale où l’intervention de la personne de confiance ou du proche n’est que consultative.
Pour prendre la décision de respecter ou non ce refus de soins, le médecin va devoir se concerter avec son équipe médicale et soignante, demander l’avis médical motivé d’un confrère. Une fois la concertation de l’équipe et la consultation du confrère médecin, le médecin prend une décision qui doit prendre en compte l’avis de la personne de confiance ou du proche.
... which says that if the patient isn't in a state to express their will (e.g. drunk, comatose, unconscious) the doctor must notify the patient's "personne de confiance" or failing that someone else close to them. If that person refuses in the name of the patient, then the doctor must put in place a "collegial" process where the intervention of the kin is merely consultative. To decide whether to respect the refusal of treatment the doctor will have to decide in concert with their medical and treatment team and ask advice from a colleague (and then decide, taking advice into account).
In other words, the kin or person of confidence (in other countries may be a.k.a. "guardian") may refuse treatment and their refusal will be taken into account and yet might not be the final decision -- the final decision might be overruled by a quorum of doctors.
There may also be an "advanced directive" previously written by the patient. The doctor may ask the patient or kin) whether there is such a directive -- and if there is, then the directive will have some weight that's similar to the weight of a kin's input (i.e. the doctor will consult it, but isn't in every case necessarily bound by it).