Messaging service WhatsApp claimed a major legal victory over Israeli spyware firm NSO Group on Friday after a federal judge ruled that NSO was liable under federal and California law for a 2019 hacking spree that breached over 1,000 WhatsApp users.

It’s a rare legal win for activists who have sought to rein in companies that make powerful spyware, or software capable of surveilling calls and texts, that has reportedly been used on journalists, human rights advocates and political dissidents worldwide.

The case will now go to trial on the question of what damages NSO Group owes Meta-owned WhatsApp, Judge Phyllis Hamilton of the Northern District of California wrote in her ruling on Friday granting WhatsApp’s motion for partial summary judgment.

The landmark case began in 2019, when WhatsApp filed suit accusing NSO Group of breaking a federal anti-hacking law, alleging that the company’s flagship custom malware, Pegasus, was used on human rights advocates and journalists in a sweeping attack in the spring of that year.

NSO Group did not immediately return a request for comment on Friday evening. The company has previously denied wrongdoing and said that its products are used to fight crime and terrorism.