29. Like the Government and the Delegate, the Court points out, firstly, that it is primarily for the national authorities, notably the courts, to interpret and apply domestic law (see, among many other authorities, the Malone judgment previously cited, Series A no. 82, p. 36, § 79, and the Eriksson judgment of 22 June 1989, Series A no. 156, p. 25, § 62). It is therefore not for the Court to express an opinion contrary to theirs on whether telephone tapping ordered by investigating judges is compatible with Article 368 of the Criminal Code. For many years now, the courts – and in particular the Court of Cassation – have regarded Articles 81, 151 and 152 of the Code of Criminal Procedure as providing a legal basis for telephone tapping carried out by a senior police officer (officier de police judiciaire) under a warrant issued by an investigating judge.
Settled case-law of this kind cannot be disregarded. In relation to paragraph 2 of Article 8 (art. 8-2) of the Convention and other similar clauses, the Court has always understood the term „law” in its „substantive” sense, not its „formal” one; it has included both enactments of lower rank than statutes (see, in particular, the De Wilde, Ooms and Versyp judgment of 18 June 1971, Series A no. 12, p. 45, § 93) and unwritten law. The Sunday Times, Dudgeon and Chappell judgments admittedly concerned the United Kingdom, but it would be wrong to exaggerate the distinction between common-law countries and Continental countries, as the Government rightly pointed out. Statute law is, of course, also of importance in common-law countries. Conversely, case-law has traditionally played a major role in Continental countries, to such an extent that whole branches of positive law are largely the outcome of decisions by the courts. The Court has indeed taken account of case-law in such countries on more than one occasion (see, in particular, the Müller and Others judgment of 24 May 1988, Series A no. 133, p. 20, § 29, the Salabiaku judgment of 7 October 1988, Series A no. 141, pp. 16-17, § 29, and the Markt Intern Verlag GmbH and Klaus Beermann judgment of 20 November 1989, Series A no. 165, pp. 18-19, § 30). Were it to overlook case-law, the Court would undermine the legal system of the Continental States almost as much as the Sunday Times judgment of 26 April 1979 would have „struck at the very roots” of the United Kingdom’s legal system if it had excluded the common law from the concept of „law” (Series A no. 30, p. 30, § 47). In a sphere covered by the written law, the „law” is the enactment in force as the competent courts have interpreted it in the light, if necessary, of any new practical developments.
In sum, the interference complained of had a legal basis in French law.
Curtea Europeană a Drepturilor Omului
(Hotărârea din data de 24 aprilie 1990, Kruslin împotriva Franței, CE:ECHR:1990:0424JUD001180185)