A federal judge on Friday lifted a freeze on a ruling that enforces a search warrant against Microsoft Corp. for customer email stored in a company data center in Ireland.

Microsoft could refuse to comply with the July 31 ruling by Chief U.S. District Judge Loretta Preska in Manhattan, forcing her to find the company in contempt. The company could then appeal.

Microsoft could also ask the Second U.S. Circuit Court of Appeals to review her Friday ruling, and to suspend it pending review.

"Microsoft will not be turning over the emails, and plans to appeal," A spokesman for Microsoft said.

The search warrant was issued as part of a criminal investigation whose details remain secret. It is unclear whether the customer targeted by the Justice Department is located in the U.S.