The case stems from a complaint against Facebook lodged at Ireland's data protection authority by Austrian right-to-privacy activist and law student Max Schrems.
The complaint focused on a landmark deal reached by the European Commission with Washington 15 years ago that allows thousands of businesses operating in the EU to send the private data of Europeans to servers in the US.
That 2000 data sharing deal, known as Safe Harbour, "is invalid", said the advocate general's recommendation.
But in a strong-worded opinion, the court's advisor Yves Bot singled out the US government for the "large scale" hoarding of European citizens private data.
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Accordingly, Bot said EU member states such as Ireland have the power to probe and even suspend the transfer of information with the United States when the privacy of European citizens is undermined.
The case centred on Ireland where major US web giants including Facebook and Apple have set up headquarters to take advantage of tax laws.
Schrems, who says he remains a fan of Facebook, welcomed the opinion in a tweet.