The United States government has appealed to its own Supreme Court in a case involving US law enforcement's efforts to gain access to emails held on Microsoft servers in Dublin.
The four-year long battle in a drugs case has major implications for cloud computing and for privacy rights worldwide.
Microsoft said at the weekend the US justice department had asked the court to reconsider a legal decision, in a case brought by Microsoft, which found that US warrants cannot be unilaterally applied to email in other countries.
Microsoft had been challenging a warrant seeking emails belonging to an EU citizen and stored the server in Ireland. The nationality of the person concerned has not been disclosed.
In January this year, a US federal appeals court refused to reconsider its earlier landmark decision forbidding the US government from forcing Microsoft and other firms to turn over customer emails stored on servers outside the US.
Cloud computing
A vote by the second US circuit court of appeals in New York in January let stand a decision of July last year that was seen as a victory for privacy advocates and for technology companies offering cloud computing and other services worldwide.
But the dissenting judges at the time said that a unanimous decision by the initial three-judge panel could hamstring law enforcement, and called on the US supreme court or Congress to reverse it.
Microsoft president and chief legal officer Brad Smith said in a blog post at the weekend that the path the US department of justice was now trying to extend "in parallel to legislative progress" sought to require the supreme court to decide "how a law written three decades ago applies to today's global internet".
He also noted that a new European data protection regulation would come into effect in less than a year.
