The paper shows the ECtHR’s practice of making references to judicial decisions made by the US Supreme Court. This issue is part of the problem of taking, by the courts in the decision-making process, foreign law into account as well as the wider phenomenon of the so-called judicial globalization. The quantitative study of the Strasbourg case law made it possible to draw a number of conclusions. First, although the ECtHR’s judgments which contain references to decisions of the highest court of the United States constitute a proportionally small fraction of all judgments, the absolute number of cases where the Strasbourg Court has made references to American case law is far from being small. Secondly, over the past decades, the process of making use of the US Supreme Court decisions by the Strasbourg Court has been noticeably intensified. Thirdly, statistically twice as often, the US Supreme Court decisions are referred to by individual ECtHR judges as authors of separate (dissenting or concurring) opinions than the Court itself. Fourth, the composition of the Court, i.e. whether it sits as a Chamber or as a Grand Chamber, does not have an impact on the operationalization of the issue in question. Fifthly, the readfilled by the American Civil Liberties Union (ACLU) on behalf of the Wikimedia Foundation and several other organizations against the National Security Agency (NSA), the US Department of Justice (DOJ) and others, alleging mass surveillance of Wikipedia users carried out by the NSA. The lawsuit states that the upstream surveillance system violates the first amendment to the United States Constitution, which protects freedom of speech, and the fourth amendment to the United States Constitution, which prohibits unjustified searches and seizures. The ACLU lawsuit was filled on behalf of almost a dozen educational, legal, human rights-related and media organizations which jointly engage in trillions of confidential online communications and have been harmed by upstream supervision. Pre-surveillance procedures hinder the plaintiffs’ ability to ensure basic confidentiality of their communications with key contacts abroad – including journalists, co-workers, clients, victims of human rights abuses, and tens of millions of people who read and edit Wikipedia pages. Pre-surveillance procedures, which, as the government claims, are authorized by the Section 702 of the FISA Amendment Act, aim to trap all the international communications of Americans, including emails, web browsing content and search engine queries. With the help of companies such as Verizon and AT&T, the NSA has installed monitoring devices on the Internet – a backbone network, a network of high-capacity cables, switches and routers allowing the flow of the Internet traffic. These goals, chosen by intelligence analysts, are never approved by any court, and the existing restrictions are weak and full of exceptions. According to Section 702, the NSA may attack any foreigner who is outside the United States and may provide “intelligence from abroad”. The number of people under surveillance is huge and includes journalists, academic researchers, corporations, social workers, entrepreneurs and other people who are not suspected of any misconduct. After the victory of Wikimedia in the fourth circuit in May 2017, the case returned to the district court where Wikimedia was looking for documents and testimonies submitted by the Supreme Administrative Court. The government refused to comply with many requests for a disclosure of Wikimedia, citing the “privilege of state secrecy” to hide the basic facts of both Wikimedia as well as the court. Wikimedia contested the government’s unjustified use of confidentiality in order to protect its supervision from surveillance, but in August 2018 the District Court upheld it. Their work is necessary for the functioning of democracy. When their sensitive and privileged communication is being monitored by the US government, they cannot work freely and their effectiveness is limited – to the detriment of Americans and others around the world. Therefore, mass surveillance leads to social self-control, but in the most undesirable form which means restriction in exercising one’s own rights, including freedom of expression, for fear of sanctions on the part of public authorities. In this way, the measures known from totalitarian regimes are introduced into a democratic state. At the same time, this process happens in a secret way, because formally, the individual still has the same rights and freedoms. In this way, mass surveillance causes damage not only to single individuals, but to the entire state as it undermines the foundations of its system. Not without reason, according to the well-established jurisprudence of the ECtHR, the primary purpose of the legal safeguards established for the secret surveillance programs conducted by states is to reduce the risk of abuse of power. However, is it possible to establish such safeguards in the case of mass surveillance programs? In accordance with the standards introduced by the ECtHR, statutory provisions should specify at least the category of offences that may involve authorization of the use of surveillance measures, as well as a limitation on the maximum duration of their application. In the case of mass surveillance, it is no longer possible to fulfil the first of the indicated safeguards, because the essence of the use of this type of measures is to intercept all communications, and not only communications concerning persons suspected of committing specific crimes. However, the reasons for the repeated belief that non-offenders should not be afraid of surveillance are also worth of detailed analysis. In fact, the supporters of this point of view believe that information which can be obtained about them does not reveal secrets they would not like to share with others. This belief completely overlooks one of the most important features of mass surveillance which is acquisition of data from various sources and their aggregation and correlation, and in the final stage – drawing new conclusions. As a rule, these conclusions go beyond the original scope of information, thus they create new knowledge about the persons subject to surveillance. It can be the knowledge about their preferences (not only shopping, but also e.g. political or sexual), expected behavior, profile of decision-making, but also the circle of friends or existing social relations. The process of acquiring new his/her nationality and the type of legal culture of his/her home country. On the other hand, the distinction between judges from the West and East of Europe is of some significance. Finally, the communication between the European Court of Human Rights and the US Supreme Court is characterized by a clear asymmetry, in the sense that the judgments of the Strasbourg Court were referred to in just a few decisions of the American court. In the author’s view, the American case law may only play a subsidiary role in the comparative analysis of the ECtHR. The primary reference point for the Strasbourg Court should be the European Convention on Human Rights, case-law developed by that Court and the law of the Member States of the Council of Europe.