The Commissioner chose to ignore the complaint because the two companies were protected by the safe harbour rules which allowed data to be packed off to the US where it could be sniffed by US spooks.

Now the Irish High Court has quashed that decision and start investigating. This is mostly because Schrems' won his lengthy battle for an audit to the European Court of Justice which basically rendered the safe harbour rules null and void.

The DPC has promised to investigate the original complaint as quickly as possible. Judge Gerard Hogan said: "The parties are agreed that the commissioner's decision must be quashed. That's not in dispute."

"The commissioner is obliged now to investigate the complaint ... and I've absolutely no doubt that she will proceed to do so," he said.

Judge Hogan said Schrems' landmark challenge over data transfer was possibly the most important ruling of the ECJ in years. He also told the court it "transcended international law".

Schrems was concerned that once in the US, Facebook and Apple was not adequately protecting the data it moved there under Safe Harbour from US intelligence agencies' surveillance programmes, as it was required to do.