The UK is a party to the European Convention for the Protection of Human Rights and Fundamental Freedoms (ECHR), a treaty of the Council of Europe. The European Court of Human Rights, which hears individual petitions against rights violations, can declare UK law incompatible with the Convention, which usually leads to parliamentary amendment or further discussion by the European Court in later cases appealed from the UK courts. The UK’s Human Rights Act 1998 requires public authorities to act in accordance with the Convention rights.
Article 8 of the Convention contains the following protections for everyone within the jurisdiction of the Council of Europe’s member states:
- Everyone has the right to respect for his private and family life, his home and his correspondence.
- There shall be no interference by a public authority with the exercise of this right except such as is in accordance with the law and is necessary in a democratic society in the interests of national security, public safety or the economic well-being of the country, for the prevention of disorder or crime, for the protection of health or morals, or for the protection of the rights and freedoms of others. 
The Court has developed general principles for restrictions on rights. These must be based on published, clear and specific legal rules; serve a legitimate aim in a democratic society; be “necessary” and “proportionate” to that aim; not involve discrimination based on race, colour, sex, language, religion, political or other opinion, national or social origin, nationality, property, birth or other status; not confer excessive discretion on the relevant authorities; and be subject to effective safeguards and remedies.
In his review, David Anderson QC considered the attitude of the European Court of Human Rights to the use of investigatory powers by signatory states including the UK, in relation to the right to privacy set down in Article 8. Anderson suggests that in recent cases, the Court has not tended to distinguish between intercepted communications and the use of communications data. A more salient distinction however is that of bulk collection practices versus individual instances of surveillance, “because of the sheer number of individuals whose private lives are interfered with”  in the former case. Thus Anderson summarises the Court’s view that “while bulk is not in itself a disproportionate interference with the right to respect for private life”, as set down in Article 8, nonetheless the practice “will be assessed against a higher standard than individual interferences with the right to privacy. The justification for that interference, and the safeguards in place to prevent abuse, will need to be more compelling if the requirements of Article 8(2) are to be satisfied.”
 European Convention on Human Rights, accessible at: http://www.echr.coe.int/Documents/Convention_ENG.pdf
 David Anderson Q.C., ‘A question of trust’, Report of the Investigatory Powers Review, July 2015, p.78
 Ibid, p.79