Microsoft Relevant Products/Services is fighting back attempts by the U.S. government to access customers' emails stored in its Irish data Relevant Products/Services centers.

The warrant was issued last December by a magistrate judge in New York as part of a drug trafficking investigation. Microsoft, which appealed the warrant and lost in April, is again beginning legal proceedings saying that because the information was stored overseas they were beyond the reach of a domestic search warrant.

"The government cannot seek and a court cannot issue a warrant allowing federal agents to break down the doors of Microsoft's Dublin facility." Microsoft's lawyers argued that Congress had never authorized U.S. courts to issue warrants that reach outside of U.S. territory.

Microsoft is debating the interpretation of the term "warrant" in the Electronic Communications Privacy Act. The Redmond-based company said that the court argued that it was issuing a hybrid between a warrant and subpoena and not a search warrant. Microsoft contends that courts in the U.S. cannot issue warrants for information held outside the country and in subpoenas, the onus is on the target of the investigation to hand over the information, not Microsoft.

Privacy advocates have thrown their weight behind Microsoft. The Electronic Frontier Foundation is working on a brief supporting Microsoft and Verizon has also filed a brief, mirroring Microsoft's objections.

"United States search warrants do not have extraterritorial reach," said Lee Tien, a lawyer for the Electronic Frontier Foundation. "The government is trying to do an end run."

The Justice Department was swift in its response issuing a filing by Preet Bharara, United States attorney for the Southern District of New York, saying that technology companies cannot hide behind technicalities invoking physical search warrants and digital ones. He added that they cannot avoid complying with a search warrant by storing information overseas.

"The US government should stop trying to force tech companies to circumvent treaties by turning over data in other countries. Under the Fourth Amendment of the US Constitution, users have a right to keep their email communications private. We need our government to uphold Constitutional privacy protections and adhere to the privacy rules established by law," wrote Microsoft's chief counsel Brad Smith in a blog post.

"That's why we recently went to court to challenge a search warrant seeking content held in our datacenter in Ireland. We're convinced that the law and the US Constitution are on our side, and we are committed to pursuing this case as far and as long as needed."