Microsoft's challenge to a U.S. warrant seeking a customer's email stored abroad is one of the key battles in the debate about privacy and the government's reach in the age of cloud computing.

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A federal appeals court has declined to review Microsoft’s refusal to comply with a U.S. search warrant seeking a customer’s emails stored abroad, letting stand a ruling hailed by civil-liberties groups and technology industry boosters as a victory for privacy.

The 2nd U.S. Circuit Court of Appeals, in a 4-4 vote announced on Tuesday, declined take up the Justice Department’s appeal of Microsoft’s July victory before a three-judge panel in the same court.

The case is among the highest profile of technology-industry challenges to the reach of law enforcement in cyberspace. It began in 2013, when prosecutors in New York served Microsoft a warrant seeking the contents of an MSN email account as part of a drug-trafficking investigation.

Microsoft, after discovering the contents of the email account were stored in an Irish data center, challenged the warrant, arguing it amounted to an international seizure that exceeded the government’s authority. Prosecutors should ask the Irish authorities instead, the company argued.

The government said it had the authority to compel a U.S. internet service provider to grab customer data, regardless of where it was stored, and that Microsoft’s position could help criminals seeking to evade government scrutiny.

The government won the first two rounds in federal court, before a 2-1 decision in Microsoft’s favor by the 2nd Circuit panel.

The Justice Department requested a new hearing before the full circuit, resulting in the 4-4 deadlock that lets the prior ruling stand. The four dissenting judges each authored a separate opinion.

“We are reviewing the decision and its multiple dissenting opinions and considering our options,” said Peter Carr, a Justice Department spokesman.

Brad Smith, Microsoft’s president and chief legal officer, said in a statement that the company welcomed the decision, and repeated his call for the government to update the decades-old statutes governing prosecutors’ access to digital material.

“This decision puts the focus where it belongs, on Congress passing a law for the future rather than litigation about an outdated statute from the past,” he said.