The case began in 2013, when U.S. prosecutors got a warrant to access emails in a drug trafficking investigation. The data was stored on Microsoft servers in Ireland.
Microsoft turned over information it had stored domestically but contended U.S. law enforcement couldn't seize evidence held in another country. It said if forced to do so, it would lead to claims from other countries about data stored here.
A judge upheld the warrant, but a panel of the U.S. Court of Appeals for the 2nd Circuit overturned the ruling. The full circuit then split evenly on whether that decision was correct.
The Justice Department asked the Supreme Court to reverse the lower courts. It said the decision conflicts with past decisions in lower courts that "a domestic recipient of a subpoena is required to produce specified materials within the recipient's control, even if the recipient stores the materials abroad."