Telecoms operators in the European Union may be required to keep customer communications information provided that it will not unduly interfere with secrecy and is strictly needed to fight serious offense, an advisor to the top EU court said on Tuesday.

While non-binding, the opinions are usually followed by the court in most cases.

Nevertheless, national governments may oblige telecoms operators so long as there are stringent safeguards to protect privacy, the advocate general said to keep communications data.

Islamist militant strikes in Belgium and France have reinvigorated calls for security agencies to be granted greater powers.

In a statement summarising the advisor’s opinion, the ECJ said national data retention laws must contain “availability, foreseeability and acceptable protection against arbitrary interference”.

The advocate general said that interference with essential rights could only be warranted to fight serious offense, “whereas fighting common offences and the smooth conduct of proceedings other than criminal proceedings are not”.

Info retention must also be “strictly required” for fighting serious offense, meaning there can be no successful choice that’s less intrusive.

A legal challenge filed against a British surveil law passed. An Investigatory Powers bill was later passed by British lawmakers.

Likewise, Swedish telecoms operator Tele2 had told its regulator that keeping information would cease after the EU Data Retention Directive was struck down by the ECJ.