The Court of Appeal has ruled that a spying law rushed through Parliament by Theresa May as Home Secretary in 2014 was unlawful.
Existing investigatory powers have been placed under the spotlight by a judgment handed down today regarding the use of the UK's surveillance apparatus to investigate non-serious crimes.
The Data Retention and Investigatory Powers Act 2014 (DRIPA) was rushed through Parliament as "emergency" legislation in 2014, with MPs given only one day to debate it.
It was challenged by Labour MP Tom Watson and Conservative MP David Davis alongside campaign group Liberty and eventually found unlawful by the High Court and the EU Court of Justice (CJEU).
Although one of the founding members of the action, David Davis MP took his name off of the challenge after being named Secretary of State for Exiting the European Union.
At the time of the CJEU, the Home Office said it was "disappointed with the judgment" which established that the UK's data retention laws - which now force ISPs to collect and store everybody's internet activity for an entire year - were too broad.
Campaigners have warned about the abuse of anti-terror laws by authorities in the UK for many years, with councils using investigatory powers to investigate dog fouling, fly tipping and breaches of the smoking ban.
The Court of Appeal has found that DRIPA was in breach of British people's rights because it did not sufficiently restrict access to the data that is collected about them, and allowed it to be used to investigate non-serious crime.
The Court also found that the law did not protect the public by requiring the police and public bodies to get a warrant to access the data, but instead were allowed to sign-off on this access themselves.
DRIPA expired at the end of 2016 and was replaced by the Investigatory Powers Act (IP Act), which has now begun to come into force.
Liberty is also challenging the IP Act in a case to be heard before the High Court later this year, as the British legal system attempts to establish how civil liberties can be respected in regards to the public's activities online.
Martha Spurrier, the director of Liberty, said: "Yet again a UK court has ruled the Government's extreme mass surveillance regime unlawful.
"This judgment tells ministers in crystal clear terms that they are breaching the public's human rights. The latest incarnation of the Snoopers' Charter, the Investigatory Powers Act, must be changed.
"No politician is above the law. When will the Government stop bartering with judges and start drawing up a surveillance law that upholds our democratic freedoms?"
The Home Office was not immediately able to comment.