1. States Parties shall assure to the child who is capable of forming his or her own views the right to express those views freely in all matters affecting the child, the views of the child being given due weight in accordance with the age and maturity of the child.  

• 100. Children, including young children, should be included in decision-making processes, in a manner consistent with their evolving capacities. They should be provided with information about proposed treatments and their effects and outcomes, including in formats appropriate and accessible to children with disabilities”.

• 101. States parties need to introduce legislation or regulations to ensure that children have access to confidential medical counselling and advice without parental consent, irrespective of the child’s age, where this is needed for the child’s safety or well-being. Children may need such access, for example, where they are experiencing violence or abuse at home, or in need of reproductive health education or services, or in case of conflicts between parents and the child over access to health services. The right to counselling and advice is distinct from the right to give medical consent and should not be subject to any age limit. 

• 102. The Committee welcomes the introduction in some countries of a fixed age at which the right to consent transfers to the child, and encourages States parties to give consideration to the introduction of such legislation. Thus, children above that age have an entitlement to give consent without the requirement for any individual professional assessment of capacity after consultation with an independent and competent expert. However, the Committee strongly recommends that States parties ensure that, where a younger child can demonstrate capacity to express an informed view on her or his treatment, this view is given due weight.

• 103.  Physicians and health-care facilities should provide clear and accessible information to children on their rights concerning their participation in paediatric research and clinical trials. They have to be informed about the research, so that their informed consent can be obtained in addition to other procedural safeguards.

 CHAPTER V – Protection of persons not able to consent to research 

Article 15 – Protection of persons not able to consent to research

1. Research on a person without the capacity to consent to research may be undertaken only if all the following specific conditions are met:

• i) the results of the research have the potential to produce real and direct benefit to his or her health;
• ii) research of comparable effectiveness cannot be carried out on individuals capable of giving consent;
• iii) the person undergoing research has been informed of his or her rights and the safeguards prescribed by law for his or her protection, unless this person is not in a state to receive the information;
• iv) the necessary authorisation has been given specifically and in writing by the legal representative or an authority, person or body provided for by law, and after having received the information required by Article 16, taking into account the person’s previously expressed wishes or objections. An adult not able to consent shall as far as possible take part in the authorisation procedure. The opinion of a minor shall be taken into consideration as an increasingly determining factor in proportion to age and degree of maturity;
• v) the person concerned does not object.

(...)

Within the European Union, EU Regulation 536/2014 on clinical trials on medicinal products for human use establishes that the explicit wish of a minor who is capable of forming an opinion and assessing the information, to refuse participation in, or to withdraw from, the clinical trial at any time, is to be respected by the investigator.

Article 32 Clinical trials on minors

1. A clinical trial on minors may be conducted only where, in addition to the conditions set out in Article 28, all of the following conditions are met: 

• (a) the informed consent of their legally designated representative has been obtained; 
• (b) the minors have received the information referred to in Article 29(2) in a way adapted to their age and mental maturity and from investigators or members of the investigating team who are trained or experienced in working with children; 
• (c) the explicit wish of a minor who is capable of forming an opinion and assessing the information referred to in Article 29(2) to refuse participation in, or to withdraw from, the clinical trial at any time, is respected by the investigator; (…) 

2. The minor shall take part in the informed consent procedure in a way adapted to his or her age and developmental maturity.
3. If during a clinical trial the minor reaches the age of legal competence to give informed consent as defined in the law of the Member State concerned, his or her express informed consent shall be obtained before that subject can continue to participate in the clinical trial. 

The Explanatory Report to the Oviedo Convention  (paragraphs 56-62) elaborates that the possibility to act without the authorisation of the legal representative is restricted to :

• emergencies which prevent the practitioner from obtaining the appropriate consent and is limited solely to medically necessary interventions which cannot be delayed. Interventions for which a delay is acceptable are excluded;
• the intervention must be carried out for the immediate benefit of the individual concerned;
• in emergency situations health care professionals must make every reasonable effort to determine what the patient would want;
• when persons have previously expressed their wishes, these shall be taken into account. Nevertheless, taking previously expressed wishes into account does not mean that they should necessarily be followed;
• these provisions apply both to persons who are capable and to persons who are unable either de jure or de facto to give consent. 

Where, due to the urgency of the situation, caused by a sudden life-threatening or other sudden serious medical condition, the subject is unable to provide prior informed consent and to receive prior information on the clinical trial, and it is not possible to obtain informed consent prior to the intervention, patients may be enrolled in the clinical trial under the following conditions:

• the clinical trial relates directly to the medical condition because of which it is not possible within the therapeutic window to obtain prior informed consent from the subject or from his or her legally designated representative; 
• there are scientific grounds to expect that participation of the subject in the clinical trial will have the potential to produce a direct clinically relevant benefit for the subject resulting in a measurable health-related improvement;
• the clinical trial poses a minimal risk to, and imposes a minimal burden on, the subject in comparison with the standard treatment of the subject's condition.

Any previously expressed objection by the patient should be respected, and informed consent from the subject or from his/her legally designated representative should be sought without undue delay and the information shall be given as soon as possible to the subject and to his/her legally designated representative.