Key paragraph(s) can be found below the document.
229. The Court has held on several occasions that the reference to “foreseeability” in the context of interception of communications cannot be the same as in many other fields. Foreseeability in the special context of secret measures of surveillance, such as the interception of communications, cannot mean that an individual should be able to foresee when the authorities are likely to intercept his communications so that he can adapt his conduct accordingly. However, especially where a power vested in the executive is exercised in secret, the risks of arbitrariness are evident. It is therefore essential to have clear, detailed rules on interception of telephone conversations, especially as the technology available for use is continually becoming more sophisticated. The domestic law must be sufficiently clear to give citizens an adequate indication as to the circumstances in which and the conditions on which public authorities are empowered to resort to any such measures (…).
230. Moreover, since the implementation in practice of measures of secret surveillance of communications is not open to scrutiny by the individuals concerned or the public at large, it would be contrary to the rule of law for the discretion granted to the executive or to a judge to be expressed in terms of an unfettered power. Consequently, the law must indicate the scope of any such discretion conferred on the competent authorities and the manner of its exercise with sufficient clarity to give the individual adequate protection against arbitrary interference (…).
231. In its case-law on secret measures of surveillance, the Court has developed the following minimum safeguards that should be set out in law in order to avoid abuses of power: the nature of offences which may give rise to an interception order; a definition of the categories of people liable to have their telephones tapped; a limit on the duration of telephone tapping; the procedure to be followed for examining, using and storing the data obtained; the precautions to be taken when communicating the data to other parties; and the circumstances in which recordings may or must be erased or destroyed (…).
233. Review and supervision of secret surveillance measures may come into play at three stages: when the surveillance is first ordered, while it is being carried out, or after it has been terminated. As regards the first two stages, the very nature and logic of secret surveillance dictate that not only the surveillance itself but also the accompanying review should be effected without the individual’s knowledge. Consequently, since the individual will necessarily be prevented from seeking an effective remedy of his or her own accord or from taking a direct part in any review proceedings, it is essential that the procedures established should themselves provide adequate and equivalent guarantees safeguarding his or her rights. In addition, the values of a democratic society must be followed as faithfully as possible in the supervisory procedures if the bounds of necessity, within the meaning of Article 8 § 2, are not to be exceeded. In a field where abuse is potentially so easy in individual cases and could have such harmful consequences for democratic society as a whole, it is in principle desirable to entrust supervisory control to a judge, judicial control offering the best guarantees of independence, impartiality and a proper procedure (…).