The court in Karlsruhe had already taken action this March against the use of data stockpiled by internet and telephone companies for criminal investigations, saying the law was too broad and risked “grave dangers” to personal privacy.

At that time, the court said data could be saved for six months and used for serious crime investigations where authorities could prove concrete suspicions for criminal offence, which included murder, theft, child pornography, money laundering, corruption, tax evasion and fraud. But now the court has decided the data can be used only in cases of danger to the public – and then “only with limited conditions,” a statement said.

These conditions include situations where calling up the data could “defend against an urgent danger to the life, limb or freedom of a person; the stability of or security of Germany or another country; or to defend against intended danger,” the statement said.

The high court also intensified rules for how news agencies will be allowed to access personal data in its decision.

The now altered data collection law went into effect on January first, but came into question in response to a class-action suit filed by some 34,000 German citizens.