The U.S. Supreme Court has agreed to hear the Justice Department's challenge in an ongoing legal battle over whether data stored by American companies overseas is covered by a U.S. warrant.
A panel of the New York-based 2nd U.S. Circuit Court of Appeals had ruled prosecutors couldn't obtain the emails, which were stored exclusively on a server in Ireland.
The DoJ has argued that it should have a right to access data stored overseas in order to protect against national security threats, while Microsoft viewed this approach as reaching too far and with ramifications for reciprocal rulings with other countries.
It puts everyone's emails at risk - if the USA government can unilaterally use a warrant to seize emails outside the United States, what's to stop other governments from acting unilaterally to seize emails stored inside the United States?
The unidentified person at the center of the Supreme Court case registered for his account as a resident of Ireland, according to one of the lower court opinions.
The case, United States v. The Justice Department says that this ruling has hampered its investigative abilities in the digital age.
Microsoft says its policy at the time of the search warrant was to store email content in the data center nearest to the customer's self-declared country of residence, while keeping account information on US servers.
"We will continue to press our case in court that the Electronic Communications Privacy Act (ECPA) - a law enacted decades before there was such a thing as cloud computing - was never meant to reach within other countries' borders", Microsoft's legal whizz Brad Smith wrote in a blog post today.
It contradicts the basic premise that before a US statute reaches across another country's borders, it should be clear that's what Congress intended when it passed the law.
In the Microsoft dispute, the Justice Department asked the appeals court to rehear the case but in January the full court split 4-4 on whether to do so, leaving the original decision intact. The law authorizes search warrants when there is probable cause that the emails are evidence of a federal crime.
In 2010, the Justice Department and 17 states sued several credit card companies, saying that their steering practices had violated the antitrust laws. An appeals court eventually ruled that Microsoft didn't have to supply the data to law enforcement.
The Justice Department says the logic behind the appeals court decision would apply even if the account holder were a US citizen living and committing crimes in this country. Officials obtained a search warrant, but Microsoft refused to turn over the information, taking the matter to court instead.