RIVADULLA DURÓ v. SPAIN DECISION constitutional significance. The Court has found that the requirement to justify the special constitutional significance of such an appeal is in accordance with the Convention (see Arribas Antón v. Spain, no. 16563/11, §§ 45-48, 20 January 2015). It has also considered that subjecting the admissibility of an amparo appeal to the existence of objective circumstances and their justification by the applicant, these being criteria provided for by law and interpreted in constitutional case-law, is not in itself disproportionate (ibid.). 20. Subsequently, noting that the machinery of protection established by the Convention is subsidiary to the national systems safeguarding human rights, the Court has reiterated that those who wish to invoke its supervisory jurisdiction as concerns complaints against a State are obliged to use first the remedies provided by the national legal system (see Álvarez Juan v. Spain (dec.), no. 33799/16, § 34, 29 September 2020, and Morales Rodríguez and Vázquez Moreno v. Spain (dec.), nos. 3696/16 and 4503/16, § 27, 24 November 2020). 21. The Court has held that where an applicant is responsible for an irremediable flaw, such as failure to provide any, or sufficient, justification of the particular constitutional significance of an appeal, the applicant has not properly exhausted domestic remedies. It has found that when an amparo appeal is rejected on the grounds that the applicant had not justified its special constitutional significance, or had failed to justify it adequately, this implied a lack of diligence for which the applicant alone was responsible, with the result that his or her application to the Court would be declared inadmissible for failure to exhaust domestic remedies (see Álvarez Juan, § 51, and Morales Rodríguez and Vázquez Moreno, §§ 40 and 41, both cited above). 22. The Court has nonetheless also emphasised that in cases in which an amparo appeal was declared inadmissible owing to insufficient justification of its special constitutional significance, the risk that that assessment might have involved excessive formalism could not be ruled out. Therefore, the Court considers that, while it is not its task to take the place of the Constitutional Court of a member State in assessing the admissibility criteria for an appeal, it is for the Court to verify that the assessment made by the Constitutional Court in this respect is not so formalistic as to restrict a litigant’s access to an effective remedy. The Court must therefore assess the specific circumstances of each case (see Morales Rodríguez and Vázquez Moreno, cited above, § 44). 23. However, in the present case the Court is not called upon to resolve this question, as it considers that the complaint is in any event inadmissible for the reasons set out below. 10