52) In that regard, it should be recalled that it is settled case-law that ‘the fundamental rights guaranteed in the legal order of the European Union are applicable in all situations governed by European Union law’. ( 43 ) Since Paragraph 7(4) of the BUrlG implements Council Directive 93/104/EC of 23 November 1993 concerning certain aspects of the organisation of working time, ( 44 ) which was codified by Directive 2003/88, Article 31(2) of the Charter is intended to apply in the main proceedings.

53) That clarification having been made, I consider that a national court hearing a dispute between two individuals is obliged, where it is not possible for it to interpret the applicable national law in conformity with Article 7 of Directive 2003/88, to ensure within its jurisdiction the judicial protection deriving for individuals from Article 31(2) of the Charter and to guarantee the full effectiveness of that article by disapplying if need be any contrary provision of national law. In my view, Article 31(2) of the Charter possesses the qualities needed for it to be relied on directly in a dispute between individuals in order to disapply national provisions which have the effect of depriving a worker of his right to an annual period of paid leave. I therefore propose that the Court adopt a solution similar to that which it adopted with regard to the general principle prohibiting discrimination on grounds of age, ( 45 ) and then in relation to Articles 21 and 47 of the Charter. ( 46 )

54) I would recall that, according to Article 31(2) of the Charter, ‘every worker has the right … to an annual period of paid leave’. As the Court has already pointed out, the right to paid annual leave is thus expressly set out in that article of the Charter, which Article 6(1) TEU recognises as having the same legal value as the Treaties. ( 47 )

55) It is apparent from the explanations relating to Article 31(2) of the Charter that that provision ‘is based on Directive 93/104 …, Article 2 of the European Social Charter and point 8 of the Community Charter on the rights of workers’. ( 48 ) I would recall that Directive 93/104 was subsequently codified by Directive 2003/88 and that, as is apparent from the wording of Article 7(1) of Directive 2003/88, ( 49 ) a provision from which that directive permits no derogation, every worker is entitled to paid annual leave of at least four weeks. As the Court has repeatedly held, that right to paid annual leave must be regarded as a particularly important principle of EU social law, the implementation of which by the competent national authorities must be confined within the limits expressly laid down by Directive 2003/88 itself. ( 50 )

56) It follows from the body of law thus described that the right to paid annual leave constitutes a particularly important principle of EU social law, now enshrined in Article 31(2) of the Charter and given concrete expression in Directive 2003/88.

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58) By following the analytical approach established by the Court in Association de médiation sociale, it seems to me legally justified to recognise that Article 31(2) of the Charter may be relied on directly in disputes between individuals in order to disapply national provisions having the effect of depriving workers of their right to an annual period of paid leave.

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60) The referring court stated that it was impossible to utilise the palliative for the lack of direct horizontal effect of directives, that is to say interpretation of its national law in conformity with the directive in question. The Court therefore had to ascertain, by analogy with its ruling in the judgment of 19 January 2010, Kücükdeveci, ( 53 ) whether Article 27 of the Charter, ( 54 ) alone or in conjunction with the provisions of Directive 2002/14/EC, ( 55 ) could be relied on in a dispute between individuals in order not to apply, where appropriate, the national provision which is not in conformity with that directive.

61) Having stated that Article 27 of the Charter was indeed applicable to the dispute in the main proceedings, the Court emphasised that, as is clear from the wording of that article, it must, to be fully effective, be given more specific expression in European Union or national law. ( 56 )

62) The Court points out, in that regard, that ‘it is not possible to infer from the wording of Article 27 of the Charter or from the explanatory notes to that article that Article 3(1) of Directive 2002/14, as a directly applicable rule of law, lays down and addresses to the Member States a prohibition on excluding from the calculation of the staff numbers in an undertaking a specific category of employees initially included in the group of persons to be taken into account in that calculation’. ( 57 )

63) This then allows the Court to note that ‘the facts of the case may be distinguished from those which gave rise to [the judgment of 19 January 2010, Kücükdeveci (C‑555/07, EU:C:2010:21),] in so far as the principle of non-discrimination on grounds of age at issue in that case, laid down in Article 21(1) of the Charter, is sufficient in itself to confer on individuals an individual right which they may invoke as such’. ( 58 )

64) The Court infers from this that ‘Article 27 of the Charter cannot, as such, be invoked in a dispute, such as that in the main proceedings, in order to conclude that the national provision which is not in conformity with Directive 2002/14 should not be applied’. ( 59 )

65) The Court adds that ‘that finding cannot be called into question by considering Article 27 of the Charter in conjunction with the provisions of Directive 2002/14, given that, since that article by itself does not suffice to confer on individuals a right which they may invoke as such, it could not be otherwise if it is considered in conjunction with that directive’. ( 60 )

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67) In Association de médiation sociale, the Court thus gave the signal that it is not possible, in disputes between individuals, to rely directly on all the provisions of the Charter in Title IV, entitled ‘Solidarity’. As a result, the Court was able to alleviate certain concerns as regards its supposed propensity broadly to accept, in disputes between individuals, the possibility of relying directly on the fundamental social rights recognised by the Charter.

68) It has been pointed out that the solution adopted by the Court in that judgment is not without its disadvantages as regards the effective protection of fundamental social rights. ( 62 ) It is also permissible to consider that Article 52(5) of the Charter not only did not rule out, but expressly permitted, the possibility before the national courts of directly relying on a provision of the Charter recognising a ‘principle’ for the purpose of reviewing the legality of national measures implementing EU law.

69) That said, it is also understandable that the Court, in its role as interpreter of the Charter and in full compliance with the principle of the separation of powers, considers itself bound by the wording of the provisions of the Charter, particularly where they recognise a right or principle whilst referring, as does Article 27 of the Charter, to the ‘cases and … the conditions provided for by Union law and national laws and practices’.

70) According to that logic, it is possible to take the view that, in Association de médiation sociale, the Court respected, without a clear statement to that effect, the summa divisio between the principles proclaimed by the Charter, the enforceability of which is limited and indirect, and the rights recognised by the Charter, which, for their part, are fully and directly enforceable.

71) Be that as it may, I shall not enter into the debate concerning the respective effects of the rights and principles recognised by the Charter and their respective degrees of enforceability, as it seems to me indisputable, in the light of the actual wording of Article 31(2) of the Charter, that an annual period of paid leave constitutes a right for workers. ( 63 )

72) I prefer to focus on what is expressly stated in Association de médiation sociale, that is to say that neither Directive 2002/14 nor Article 27 of the Charter, whether considered alone or together, may confer on individuals a right which they may directly rely on as such in a horizontal dispute.

73) In other words, the juxtaposition of the Charter provision concerned and a rule of secondary EU law intended to clarify it cannot make it possible to rely directly on that provision. ( 64 ) At the same time, it follows from the reasoning of the Court in Association de médiation sociale that the possibility of relying directly on provisions of the Charter in horizontal disputes is not excluded from the outset. Such a possibility of reliance on a provision may exist if the article of the Charter at issue is sufficient in itself to confer on individuals an individual right which they may invoke as such. ( 65 ) According to the Court, that is not the case with Article 27 of the Charter, which, as is clear from its wording, must be ‘given more specific expression in European Union or national law’ ( 66 ) in order to produce its effects in full.

74) The logic inherent in the reasoning of the Court in Association de médiation sociale thus appears to me to be based on the idea that a directive giving concrete expression to a fundamental right recognised by a provision of the Charter cannot confer on that provision the qualities needed for it to be relied on directly in a dispute between individuals, where it is found that that provision cannot in itself, either in the light of its wording or in the light of the explanations relating thereto, be recognised as having such qualities. According to that logic, it is impossible for a directive which does not have direct horizontal effect to impart that quality to a provision of the Charter.

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75) Association de médiation sociale therefore put an end to any ambiguity arising from the wording of the judgment of 19 January 2010, Kücükdeveci, ( 67 ) which referred to the possibility of relying on the ‘principle of non-discrimination on grounds of age as given expression in Directive 2000/78[/EC ( 68 )]’. ( 69 ) Was not that wording tantamount to calling into question the well-established case-law concerning the lack of direct horizontal effect of directives or even the hierarchy of norms? ( 70 ) On those points, it is clear from Association de médiation sociale that the rule arising from the judgment of 19 January 2010, Kücükdeveci, ( 71 ) is confirmed and that it is only the provision of primary law which can, where appropriate, be relied on in a dispute between individuals. ( 72 ) That judgment may, therefore, in so far as it recognises the potential possibility of relying directly on provisions of the Charter in horizontal disputes, be regarded as establishing an additional palliative for the lack of direct horizontal effect of directives. ( 73 )

76) The Court further developed that rule of case-law in its judgment of 17 April 2018, Egenberger, ( 74 ) by acknowledging the possibility, in a dispute between private individuals, of relying directly on Article 21 of the Charter, in so far as it prohibits all discrimination on grounds of religion or belief, ( 75 ) and on Article 47 of the Charter, concerning the right to effective judicial protection. ( 76 )

77) Contrary to what has sometimes been argued, recognition of the potential possibility of relying directly on provisions of the Charter in horizontal disputes, which in my view constitutes the major contribution in Association de médiation sociale, is not contrary to Article 51 of the Charter, since that recognition is intended to ensure that Member States, to which the provisions of the Charter apply, respect the fundamental rights recognised therein when implementing EU law. The fact that those rights are relied on in the context of a horizontal dispute is, from that point of view, not decisive and cannot in any event enable the Member States to avoid a finding that they have infringed the Charter in their implementation of EU law. ( 77 )

78) Accordingly, it is appropriate definitively to remove any obstacle which Article 51(1) of the Charter constitutes to the possibility of relying directly on the provisions of the Charter in disputes between individuals. Although that article provides that the provisions of the Charter ‘are addressed to the institutions, bodies, offices and agencies of the Union …, and to the Member States only when they are implementing Union law’, that article does not expressly exclude any effect of the Charter in relations between private individuals. ( 78 ) It should be added that the Court has held that several provisions of primary EU law have horizontal direct effect, although, in the light of their wording, those provisions are addressed to the Member States. ( 79 )

79) It follows from the foregoing that, in Association de médiation sociale, the Court established an analytical approach to the relationship between the protection afforded by directives and by rules protecting fundamental rights. ( 80 ) The present cases offer the Court the opportunity to supplement and clarify that analytical approach, on this occasion in relation to an article of the Charter, namely Article 31(2), which, contrary to Article 27 thereof, possesses, in my view, the qualities needed to be relied on directly in a dispute between individuals in order to disapply, where appropriate, contrary national rules.

80) In order for there to exist such a possibility of relying on it directly, the relevant provision of the Charter must, on the basis of its inherent qualities, as clearly expressed in its wording, be mandatory and sufficient in itself. ( 81 )

81) The fundamental right to an annual period of paid leave, as set out in Article 31(2) of the Charter, is undoubtedly mandatory in nature. The Court has consistently emphasised in its case-law both the importance and the mandatory nature of the right to paid annual leave, by stating that it is ‘a particularly important principle of European Union social law from which there can be no derogations’. ( 82 ) That right must therefore apply not only to the action of public authorities, but also to employment relationships established between private individuals. That criterion was taken into account by the Court in its judgment of 8 April 1976, Defrenne (43/75, EU:C:1976:56). ( 83 )

82) Moreover, as I have already stated, the relevant provision of the Charter must be sufficient in itself, ( 84 ) which means that it must not be necessary to adopt a supplementary provision of EU or national law to render applicable the fundamental right recognised by the Charter. ( 85 ) In other words, the relevant provision of the Charter requires no supplementary measure to be adopted in order directly to produce effects as regards individuals.

83) Indeed, I consider that, in the light of its wording, Article 31(2) of the Charter requires no supplementary measure to be adopted in order directly to produce effects as regards individuals. In such circumstances, the adoption of an act of secondary EU law and/or implementing measures by the Member States may certainly be useful to allow individuals to benefit in practice from the fundamental right concerned. That said, the adoption of such measures, which is not required by the wording of the relevant provision of the Charter, is not necessary in order for that provision directly to produce its effects in disputes which must be resolved by national courts. ( 86 )

84) It follows from the foregoing that, in so far as it recognises the right of every worker to an annual period of paid leave, Article 31(2) of the Charter possesses the qualities needed to be relied on directly in a dispute between individuals in order to disapply national provisions having the effect of depriving a worker of that right. That is the case, as I have already stated, with national legislation or practice which provides that the entitlement to paid annual leave is lost without conferring entitlement to an allowance in lieu of outstanding paid annual leave, and which therefore makes it impossible for the deceased’s heirs to be paid such an allowance, where the employment relationship is terminated by the death of the worker. As the Court stated, in essence, in Bollacke, such national legislation or practice has the effect of ‘retroactively leading to a total loss of the entitlement to paid annual leave itself’. ( 87 )

85) Consequently, I suggest that, in Willmeroth (C‑570/16), the Court’s answer to the question referred by the Bundesarbeitsgericht (Federal Labour Court) should be that a national court hearing a dispute between two individuals is obliged, where it is not possible for it to interpret the applicable national law in conformity with Article 7 of Directive 2003/88, to ensure within its jurisdiction the judicial protection deriving for individuals from Article 31(2) of the Charter and to guarantee the full effectiveness of that article by disapplying if need be any contrary provision of national law.

86) I shall further point out that the finding that Article 31(2) of the Charter is, in so far as it provides for the right of every worker to an annual period of paid leave, sufficient in itself to confer on individuals a right which they may rely on as such in disputes between them in a field covered by EU law does not exhaust the issue of determining the normative content of that provision.

87) In that regard, I note that one of the lessons to be learned from Association de médiation sociale is that the Explanations relating to the Charter must be taken into account in order to determine whether a provision of the Charter is capable of being relied on directly in a dispute between individuals. ( 88 ) Accordingly, those explanations must, in my view, be taken into consideration in order to identify the normative content of the directly applicable legal rule contained in Article 31(2) of the Charter. Such consideration of the Explanations relating to the Charter is, moreover, dictated by the third subparagraph of Article 6(1) TEU, according to which ‘the rights, freedoms and principles in the Charter shall be interpreted in accordance with the general provisions in Title VII of the Charter governing its interpretation and application and with due regard to the explanations referred to in the Charter, that set out the sources of those provisions’. In accordance with Article 52(7) of the Charter, ‘the explanations drawn up as a way of providing guidance in the interpretation of this Charter shall be given due regard by the courts of the Union and of the Member States’. ( 89 )

see also paras 88 - 96