BRUSSELS: Europe’s top court on Tuesday endorsed the power of national data watchdogs to pursue big tech firms even if they are not their lead regulators, in a setback for Silicon Valley companies such as Facebook.

The EU Court of Justice (CJEU) ruling could encourage national agencies to act against US tech companies such as Google, Twitter and Apple, which all have their European Union headquarters in Ireland.

Many national watchdogs in the 27-member European Union have long complained about their Irish counterpart, saying that it takes too long to decide on cases.

Ireland has dismissed this, saying it has to be extra meticulous in dealing with powerful and well-funded tech giants.

The CJEU got involved after a Belgian court sought guidance on Facebook’s challenge against the territorial competence of the Belgian data watchdog’s bid to stop it from tracking users in Belgium through cookies stored in the company’s social plug-ins, regardless of whether they have an account or not.

“Under certain conditions, a national supervisory authority may exercise its power to bring any alleged infringement of the GDPR before a court of a member state, even though that authority is not the lead supervisory authority with regard to that processing,” the EU Court of Justice (CJEU) said.

Under landmark EU privacy rules known as GDPR, Facebook faces oversight by the Irish privacy authority because it has its European head office in Ireland.

The case is C-645/19 Facebook Ireland & Others.