The case of Pietrzak and Bychawska-Siniarska and Others vs. Poland involved five Polish nationals' complaints against Polish laws authorizing secret surveillance and the retention of telecommunications, postal, and digital communications data for future use by national authorities. They claimed that there was no domestic legal remedy for those suspecting they were under surveillance to challenge its legality.

The European Court of Human Rights (ECtHR) unanimously found three violations of Article 8 (right to respect for private and family life and correspondence) of the European Convention on Human Rights (ECHR). These violations concerned the operational control regime, the retention of communications data, and the secret surveillance provisions under the Anti-Terrorism Act.

The Court determined that the secretive and extensive nature of the surveillance measures, combined with the lack of an effective review mechanism, justified examining the legislation in general. It ruled that the mere existence of such legislation interfered with the applicant's Article 8 rights. The Court concluded that the national laws lacked sufficient safeguards against excessive surveillance and undue interference with private life and that the judicial review mechanisms were inadequate. It also found that the indiscriminate retention of communications data and the unchecked application of secret surveillance under the Anti-Terrorism Act did not meet the necessary democratic society standards.