Key paragraph(s) can be found below the document.
114. […] even though telephone conversations are not expressly mentioned in Article 11 of the Convention, they are a form of communication included within the sphere of the protection of privacy. Article 11 protects conversations using telephone lines installed in private homes or in offices, whether their content is related to the private affairs of the speakers, or to their business or professional activity. [the scope of Article 11 (prohibition against arbitrary or abusive interference in the private life of individuals)]
129: Since the telephone conversations of the alleged victims were private and they had not authorized that their conversations be conveyed to third parties, the interception of the conversations by State agents constituted interference in their private life. Therefore, the Court must examine whether this interference was arbitrary or abusive in the terms of Article 11(2) of the Convention or whether it was compatible with the said treaty. As indicated previously (supra para. 116), to conform to the American Convention any interference must comply with the following requirements: (a) it must be established by law; (b) it must have a legitimate purpose, and (c) it must be appropriate, necessary and proportionate. Consequently, the absence of any of these requirements implies that the interference is contrary to the Convention.