(21)This Directive should therefore identify situations where a procedural or a substantive issue of compliance with Union law may need to be resolved and the national supervisory authorities may not be able to resolve the matter on their own. In such a situation, one of the national supervisory authorities concerned should be able to raise the issue with the ESA concerned. That ESA should act in accordance with its establishing regulation and with this Directive. It should be able to require that the national supervisory authorities concerned take specific action or refrain from action in order to settle the matter and ensure compliance with Union law, with binding effects on the national supervisory authorities concerned. In cases where the relevant legislative act of the Union confers discretion on Member States, decisions taken by an ESA should not replace the exercise of discretion by the national supervisory authorities, where that exercise is in accordance with Union law.