In its notice of appeal filing, the DOJ called on the U.S. Court of Appeals for the District of Columbia Circuit to reverse the ruling.
District Court Judge Richard Leon last week issued a major defeat for the NSA’s collection of phone metadata, calling the practice “almost Orwellian.”
Leon ordered the NSA to stop its collection of bulk phone call data, but placed his decision on hold pending a possible appeal. The judge called the NSA’s practices “likely unconstitutional.”
Days after Leon's ruling, another federal judge, William H. Pauley III, in New York upheld a separate challenge to the NSA's data collection. The American Civil Liberties Union, which brought that challenge, has also said it would appeal that ruling.
Leaks from former government contractor Edward Snowden disclosing the extent of the NSA's surveillance of phone and internet traffic sparked a firestorm of controversy.
President Obama has vowed to better balance the nation's security interests with privacy rights and is reviewing the recommendations from an outside task force that examined the surveillance programs.
Obama will announce the proposals he will enact to reform the NSA later this month.
Lawmakers have also vowed to take action if Obama fails to enact sufficient oversight of the spy agency.
But at his year-end press conference in December, Obama also said he would take “very seriously” the recommendations from the outside NSA review task force.
“There have not been actual instances where it's been alleged that the NSA acted inappropriately,” said Obama at the conference. “I have confidence in the fact that the NSA is not engaging in domestic surveillance or snooping around.
“We may have to refine this further to give people more confidence, and we need to give more confidence for the international community,” he added.