A landmark legal challenge to the State’s legislation requiring the retention of the phone and internet records of all individuals for up to two years returns to the High Court on Monday.

The action being taken by the Digital Rights Ireland (DRI) privacy lobby group follows its success in April 2014 in having the entire European regime for the retention of such personal data about more than 500 million citizens overturned by the European Court of Justice (ECJ) in Luxembourg.

DRI launched a court action against the State in 2006 questioning the legality of Irish data retention laws requiring phone companies and internet service providers to keep data about customers’ locations, calls, texts and emails, and store that information for up to two years.

The case challenged the constitutionality and the implementation of Ireland’s legislation, both the Criminal Justice (Terrorist Offences) Act 2005 and the State’s 2006 implementation of the 2006 EU data-retention directive.

In 2012, the High Court referred the case to the ECJ, asking for an opinion on the validity of the EU directive.

Invalid

In April 2014, the Luxembourg court declared the European directive invalid, saying it entailed “a wide-ranging and particularly serious interference with the fundamental rights to respect for private life and to the protection of personal data”.

“The fact that data are retained and subsequently used without the subscriber or registered user being informed is likely to generate in the persons concerned a feeling that their private lives are the subject of constant surveillance,” it said.

At that time, DRI chairman TJ McIntyre welcomed the ECJ ruling, describing it as the first assessment of mass surveillance by a supreme court since the Edward Snowden revelations.

“The ECJ’s judgement finds that untargeted monitoring of the entire population is unacceptable in a democratic society,” he said.

DRI is returning to the High Court on Monday following what a spokesman said was an “inconclusive exchange of correspondence with the State”.

It is seeking to have the remaining matters of EU law dealt with by the court following the ECJ ruling.

It is expected the case will be put forward to a date to fix a hearing in the new year.