38 GORZELIK AND OTHERS v. POLAND JUDGMENT 95. Nonetheless, that power must be used sparingly, as exceptions to the rule of freedom of association are to be construed strictly and only convincing and compelling reasons can justify restrictions on that freedom. Any interference must correspond to a “pressing social need”; thus, the notion “necessary” does not have the flexibility of such expressions as “useful” or “desirable” (see Young, James and Webster, and Chassagnou and Others, cited above). 96. It is in the first place for the national authorities to assess whether there is a “pressing social need” to impose a given restriction in the general interest. While the Convention leaves to those authorities a margin of appreciation in this connection, their assessment is subject to supervision by the Court, going both to the law and to the decisions applying it, including decisions given by independent courts. When the Court carries out its scrutiny, its task is not to substitute its own view for that of the national authorities, which are better placed than an international court to decide both on legislative policy and measures of implementation, but to review under Article 11 the decisions they delivered in the exercise of their discretion. This does not mean that it has to confine itself to ascertaining whether the respondent State exercised its discretion reasonably, carefully and in good faith; it must look at the interference complained of in the light of the case as a whole and determine whether it was “proportionate to the legitimate aim pursued” and whether the reasons adduced by the national authorities to justify it are “relevant and sufficient”. In so doing, the Court has to satisfy itself that the national authorities applied standards which were in conformity with the principles embodied in Article 11 and, moreover, that they based their decisions on an acceptable assessment of the relevant facts (see, mutatis mutandis, United Communist Party of Turkey and Others, cited above, p. 27, §§ 46-47, and Refah Partisi (the Welfare Party) and Others, cited above, § 100). (ii) Application of the above principles to the present case (α) Pressing social need 97. The Court will first determine whether there could be said to have been, at the relevant time, a “pressing social need” to take the impugned measure – namely the refusal to register the association with the description in paragraph 30 of its memorandum of association (see paragraph 22 above) – in order to achieve the legitimate aims pursued. The principal reason for the interference thereby caused with the applicants' enjoyment of their freedom of association was to pre-empt their anticipated attempt to claim special privileges under the 1993 Elections Act, in particular an exemption from the threshold of 5% of the votes normally required to obtain seats in Parliament and certain advantages in respect of the registration of electoral lists (see paragraphs 32, 36 and 41 above).