A federal judge in Northern California has denied WhatsApp’s attempt to hold NSO Group in contempt for allegedly violating a court injunction against using the messaging platform’s infrastructure to deploy spyware. Judge Phyllis Hamilton ruled Friday that WhatsApp failed to present “clear and convincing evidence” that the Pegasus spyware maker breached the order.

The ruling stems from a June appeal filed by the Meta owned messaging service, which accused NSO of mounting new spearphishing attacks against users after Hamilton had already found the company liable in a long running legal battle. Pegasus, NSO’s zero click spyware, was used to target roughly 1,400 WhatsApp users in 2019.

Hamilton had issued the injunction earlier in 2025 and fined NSO $4.4 million after agreeing that the company improperly abused WhatsApp’s infrastructure to target and, in some instances, infect devices with its surveillance tools. But in the latest ruling, the judge found WhatsApp’s supporting evidence insufficient, noting the company “took a calculated risk in choosing to limit the level of detail” it disclosed.

WhatsApp’s case rested on a declaration from Andrew Blaich, a security engineer on Meta’s threat intelligence team, who said he identified 23 new WhatsApp accounts exhibiting “technical and behavioral signatures” previously linked to NSO testing activity, including registration patterns, device information, and ties to known NSO controlled infrastructure. WhatsApp declined to detail its detection methods further, arguing that disclosure could undermine its ability to fight spyware vendors in future cases.

A Familiar Dilemma

The tension echoes Apple’s 2024 decision to drop its own lawsuit against NSO, which the company said risked exposing “vital security information.”

Digital rights advocates criticized Hamilton’s decision. Natalia Krapiva, senior tech counsel at Access Now, said forcing WhatsApp to expose its research and detection methods would hand “enormous benefits” to NSO, foreign intelligence services, exploit developers, and criminals seeking to understand how spyware is detected and how platforms defend against it.

Krapiva warned that requiring such disclosures as a precondition for accountability could effectively grant “complete impunity for the spyware industry.”

WhatsApp and NSO Group did not immediately respond to requests for comment on the ruling.