A court case has pointed out a disturbing potential privacy crisis as police could use bulk surveillance techniques as laid out in a ruling by the UK’s Investigatory Powers Tribunal.

This means that platforms employing end-to-end encryption, such as WhatsApp and Signal, could be surveilled by law enforcement if they obtain a certain warrant.

This was all revealed in an appeal heard by the Court of Appeal’s Civil Decision surrounding the National Crime Agency’s (NCA) role in the takedown of an organised crime unit operating in Europe through Operation Venetic, which was achieved through intercepting messages sent via EncroChat, an encrypted messaging system.

Working with French and Dutch Police, the NCA helped intercept around 60,000 EncroChat phones by implanting software on the devices, which aided them in identifying and arresting over 3,100 people, resulting in 1,500 convictions and seizing of illicit materials including Class A drugs and ammunition, as well as £84m in cash.

Even at the time of the Operation’s success, some were concerned over what this could mean for the sanctity of encrypted messaging services, and the appeals hearing, which represented 11 defendants, revealed potentially troubling methods of the NCA in obtaining the warrant to infiltrate the messaging platform.

In order to intercept the messages, the NCA used a targeted equipment interreference (TEI) warrant enabling French police to hack EncroChat phones of individuals with UK residency.

Typically, TEI warrants are obtained for a single operation, for instance to monitor an identified organised crime group.

In the hearing, lawyers claimed that the TEI warrant was not suitable to monitor all users of a messaging platform, stating that the targets using the publicly available technology for their suspected criminal activity was not enough justification for that type of warrant.

Though EncroChat was notably adopted by many criminal organisations to keep their communications encrypted, the platform itself is completely legal and can be used by members of the public who want to enjoy more robust privacy in their messaging. The company first launched, for instance, aiming to provide private communication for celebrities hoping to avoid their messages being hacked.

According to defence lawyers, Operation Venetic’s purpose was to gather information from EncroChat messages for multiple investigations, and the warrant application was also intended to allow UK law enforcement to continue monitoring EncroChat for future investigations.

Another issue highlighted by the appeals court shows that the NCA blurred the line between bulk and thematic warrant requirements.

Bulk interception warrants are deemed lawful for international operations when crime agencies are not entirely sure what they are looking for, and are typically used for large scale operations that without as much pre-determined targets.

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Thematic warrants have more than one subject, and often would be used to look at multiple suspects across a platform.

Lawyers argued that the NCA changed the re-named Project Venetic to Operation Venetic before applying for the bulk TEI warrant to allow them to sidestep this distinction, resulting in its ability to tap into an international platform.

The very use of TEI, over TI (targeted interception) was also questioned.

Initially, the NCA was advised by Lord David Anderson that a thematic TEI warrant would not be suitable for the operation as it did not have strong enough grounds.

The NCA did release a threat assessment of EncroChat phones in 2019, but this was also after French officials were investigation a server of the platform, which an NCA official had visited. Further, Europol already stated their intentions to access and decrypt EncroChat communications in 2019.

The threat assessment claimed that EncroChat was only used by criminals – the court questioned if this report was bias to enable the NCA to carry out its investigation and support its TEI warrant, and claimed that the IPT made a “speculative assumption” about the report.