The European Court of Human Rights has ruled that some aspects of British surveillance regimes violated the European Convention on Human Rights.
The case brought by civil liberties, human rights and journalism groups and campaigners challenged British surveillance and intelligence-sharing practices revealed by American whistleblower Edward Snowden.
The complainants suspect British and US spy agencies may have intercepted their electronic communications.
Corey Stoughton, of human rights group Liberty described Thursday’s ruling as “a major victory for those of us who think there ought to be balance in the government’s ability to engage in surveillance”.
Britain has changed its surveillance laws since the legal challenge began, passing new legislation that the government says has more privacy safeguards.
Thursday’s ruling is not final and can be appealed.