Charter – where it generally held that rights arising under Community law are not part of the fundamental rights that can be invoked by way of a constitutional complaint pursuant to Art. 93(1) no. 4a GG, § 90(1) of the Federal Constitutional Court Act (Bundesverfassungsgerichtsgesetz – BVerfGG), the First Senate no longer upholds that view when it comes to the domestic application of EU fundamental rights to the extent set out above (para. 60). A review that relies on EU fundamental rights as the applicable standard can be carried out without any difficulties on the basis of applicable procedural law (cf. §§ 90 et seq. BVerfGG). 6. To the extent that the Federal Constitutional Court relies on the fundamental rights of the Charter as the relevant standard of review, it seeks close cooperation with the Court of Justice of the European Union. 68 a) According to Art. 19(1) subpara. 1 second sentence TEU and Art. 267 TFEU, the Court of Justice of the European Union has final authority for interpreting EU law. This includes the interpretation of the fundamental rights guaranteed by the Charter and the development of principles deriving from them for their application. Yet the Federal Constitutional Court has authority to review the correct application of EU fundamental rights. In that regard, it is a domestic court of last instance within the meaning of Art. 267(3) TFEU and can, as the case may be, be obliged to bring a matter before the Court of Justice of the European Union (cf. CJEU, Judgment of 6 October 1982, Cilfit, C-283/81, EU:C:1982:335, para. 21). 69 The Federal Constitutional Court can thus only apply EU fundamental rights where a relevant question of interpretation has been clarified in the case-law of the Court of Justice of the European Union or the answer is clear from the outset based on established principles of interpretation – for instance, by drawing on the case-law of the European Court of Human Rights (ECtHR), which, in the individual case, may also define the contents of the Charter (cf. Art. 52(3) and (4) of the Charter). Where this is not the case, the Federal Constitutional Court is required to refer the respective questions to the Court of Justice of the European Union. Given that the questions of interpretation arising in this scenario are generally directly relevant for deciding a matter, referrals will have to be considered to a far greater extent than in cases where the Charter applies in addition to the Basic Law (cf. BVerfG, Order of the First Senate also issued today - 1 BvR 16/13 - paras. 43 and 44) but the Federal Constitutional Court – as it has done until now – conducts its review on the basis of German fundamental rights (cf. loc. cit., paras. 45 et seq., 154). 70 In this context, uncertainties generally cannot be resolved through recourse to domestic case-law on German fundamental rights. While fundamental rights protection under the Basic Law and under the Charter may often be congruent and principles of interpretation may be transferrable from one system to the other, caution should be exercised in this respect in light of the uniformity of EU law. In principle, the interpretation must be directly based on the fundamental rights of the Charter and the caselaw of the European courts, and links back to the overall understanding of fundamen- 71 15/36