The EU Court of Justice (CJEU) has delivered a landmark judgement effectively prohibiting mass surveillance – in a move which strikes at the heart of the UK’s recently passed Snoopers’ Charter.

The finding was delivered in response to a case brought by Labour deputy leader Tom Watson and then-backbencher David Davis surrounding bulk collection of communications by GCHQ.

Davis subsequently withdrew his name after his appointment as Brexit secretary. But at the time the two’s lawyers argued that the predecessor of the Investigatory Powers Act (Snoopers’ Charter), known as Dripa, was illegal.

They have been proven correct, with the CJEU ruling that the legislation “exceeds the limits of what is strictly necessary and cannot be considered to be justified within a democratic society.”

It added:

“The Court states that, with respect to retention, the retained data, taken as a whole, is liable to allow very precise conclusions to be drawn concerning the private lives of the persons whose data has been retained.

"The interference by national legislation that provides for the retention of traffic data and location data with that right must therefore be considered to be particularly serious. The fact that the data is retained without the users of electronic communications services being informed of the fact is likely to cause the persons concerned to feel that their private lives are the subject of constant surveillance. Consequently, only the objective of fighting serious crime is capable of justifying such interference.”

With the UK set to leave the EU, and therefore the jurisdiction of the CJEU, it’s unlikely that any changes will be made to the Snoopers’ Charter as a result of this judgement. However, Privacy International – which intervened in the case along with the Open Rights Group – reckons it should force a government rethink on certain parts of the new law.

“Today's judgment is a major blow against mass surveillance and an important day for privacy. It makes clear that blanket and indiscriminate retention of our digital histories – who we interact with, when and how and where – can be a very intrusive form of surveillance that needs strict safeguards against abuse and mission creep. Unfortunately, those safeguards are not present in the Investigatory Powers Act, which is why it’s a Snoopers’ Charter,” said Privacy International legal officer, Camilla Graham Wood.

“The court has rightly recognized that our communications data is no less sensitive than the content of our communications. This is something that the UK government has wilfully ignored, allowing a large number of public bodies to access our personal data without a warrant. The government must now urgently fix the Investigatory Powers Act, so that access to our data is properly authorized.”

The case will now be referred to the UK Court of Appeal, where the government claims it will put forward “robust arguments” about “the strength of our existing regime for communications data retention and access.”