Article 19 1. The prohibition on processing personal data concerning a person's political persuasion, as referred to in Article 16, does not apply where the processing is carried out: a. by institutions founded on political principles with respect to their members or employees or other persons belonging to the institution, provided that this is necessary to the aims of the institutions and for the achievement of their principles, or b. with a view to the requirements concerning political persuasion which can reasonably be applied in connection with the performance of duties in administrative and advisory bodies. 2. In the cases referred to under (1)(a), no personal data may be supplied to third parties without the consent of the data subject. Article 20 1. The prohibition on processing personal data concerning a person's trade union membership, as referred to in Article 16, does not apply where the processing is carried out by the trade union concerned or the trade union federation to which this trade union belongs, provided that this is necessary to the aims of the trade union or trade union federation; 2. In the cases referred to under (1), no personal data may be supplied to third parties without the consent of the data subject. Article 21 1. The prohibition on processing personal data concerning a person's health, as referred to in Article 16, does not apply where the processing is carried out by: a. medical professionals, healthcare institutions or facilities or social services, provided that this is necessary for the proper treatment and care of the data subject, or for the administration of the institution or professional practice concerned; b. insurance companies as referred to in Article 1(1)(h) of the Insurance Supervision Act 1993 (Wet toezicht verzekeringsbedrijf 1993), insurance companies as referred to in Article 1(c) of the Funeral Insurance Supervision Act (Wet toezicht natura-uitvaartverzekeringsbedrijf), and intermediaries and sub-agents as referred to in Article 1(b) and (c) of the Insurance Mediation Act (Wet assurantiebemiddelingsbedrijf), provided that this is necessary for: 1º. assessing the risk to be insured by the insurance company and the data subject has not indicated any objection thereto, or 2º. the performance of the insurance agreement; c. schools, provided that this is necessary with a view to providing special support for pupils or making special arrangements in connection with their state of health; d. institutions for probation, child protection or guardianship, provided that this is necessary for the performance of their legal duties; e. Our Minister of Justice, provided that this is necessary in connection with the implementation of prison sentences or detention measures, or