A senior European Union official has condemned a US effort to force Microsoft to hand over email stored in its Irish datacentre.

Microsoft's fight against a US search warrant involving email hosted in its Irish datacentre has gained the support of EU vice president Viviane Reding, who believes the warrant may be in breach of international law.

In a response to questions from Dutch MEP Sophia in't Veld, Reding said the warrant served to Microsoft "bypasses existing formal procedures that are agreed between the EU and the US, such as the Mutual Legal Assistance Agreement".

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Microsoft is arguing for the US government to turn to these avenues for data stored outside the US, comparing the warrant to the US government "breaking down the doors" to its Irish datacentre. It's says the warrant extends US authority outside its own jurisdiction, which Reding agrees with.

"The Commission's concern is that the extraterritorial application of foreign laws (and orders to companies based thereon) may be in breach of international law and may impede the attainment of the protection of individuals guaranteed in the Union," she said.

Reding's statement echoes arguments laid out by Apple, Cisco, AT&T, and Verizon in support of Microsoft's District Court bid to quash the warrant which, if successful, could set new boundaries for US law-enforcement investigation powers in the context of cloud computing.

The companies say that upholding the warrant "threatens a potential loss of customer confidence in US providers generally" and come against a backdrop of heightened suspicion of US technology in light of US government surveillance revealed by former NSA contractor Edward Snowden.

The companies are also concerned that disregarding existing mutual legal assistance agreements places their employees abroad at risk of foreign sanctions — a point which Reding also agrees with.

"Companies bound by EU data protection law who receive such a court order are caught in the middle of such situations where there is, as you say in your letter, a conflict of laws," she wrote.

Microsoft's first attempt to have the warrant thrown out failed in April, in part because, under the Electronic Communications Privacy Act (ECPA) the "search" itself would occur in the US. Also, law enforcement don't actually enter Microsoft's property overseas. The US government believes the law is a critical tool for online investigations.

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