The High Court has refused a request by Facebook to delay the referral of a landmark privacy case that could strike down legal instruments used by US tech companies to transfer EU users' data to the United States.
The Court has ordered the case be referred to Europe's top court.
The case is the latest to question whether methods used by technology firms such as Google and Apple to transfer data outside the 28-nation European Union give consumers sufficient protection from US surveillance.
The court ordered the case be referred to assess whether the methods used for data transfers - including standard contractual clauses and the Privacy Shield agreement - were legal.
It said the case raised well-founded concerns that there was an absence of an effective remedy in US law compatible with EU legal requirements.
A ruling by the European Court of Justice against the legal arrangements could cause major headaches for thousands of companies, which make millions of these transfers every day.
Earlier this week Facebook sought a delay to ask the Supreme Court for the right to appeal the referral, but High Court Judge Caroline Costello has refused the request and ordered the referral to be made immediately.
"I am of the opinion that the court will cause the least injustice if it refuses any stay and delivers the reference immediately to the Court of Justice," Justice Costello told the court.
Facebook said it will still seek permission from the Supreme Court to appeal the referral, but the move will not delay the ECJ's hearing of the case.
The case, taken by Austrian privacy activist Max Schrems, was heard in Ireland because it is the location of Facebook's headquarters for most of its markets outside the US.