BRUSSELS: The EU’s top court on Tuesday put limits on how European spy and security agencies could harvest troves of personal data, but said this could be done under a serious threat to national security.

At the request of the courts in France, Belgium and Britain, the European Court of Justice confirmed that “EU law precludes national legislation” that requires telcos and tech companies to carry out the “indiscriminate retention” of data, a statement said

However, it does allow for exemptions in cases of “serious threat to national security” or the “fight against serious crime”, under the supervision of a judge or an independent administrative authority. This lifting of the ban would have to be “limited in time to what is strictly necessary,” the court added. The decision will be closely looked at by privacy activists who fear wide loopholes that would allow unfettered data spying by state agencies.