Case C-474/16. Social security

Is the legal effect of an A1 certificate issued to a temporary-work agency, in accordance with Article 19 of Regulation (EC) No 987/2009 [...] laying down the procedure for implementing Regulation (EC) No 883/2004 [...] on the coordination of social security systems, by the institution designated by the Member State whose social security legislation remains applicable to the employed worker, binding, first, on the institutions and authorities of the host Member State and, secondly, on the courts of that Member State, if it is found that the conditions under which the employee pursues the activity clearly do not fall within the substantive scope of the specific rules set out in Article 12(1) and (2) of Regulation (EC) No 883/2004?