Civil rights attorneys at the American Civil Liberties Union have filed an appeal with a federal court asking the judge to outlaw the National Security Agency’s collection of phone metadata after another court deemed the method of surveillance legal.

Lawyers for the ACLU, in conjunction with their counterparts at the New York Civil Liberties Union, filed papers at the 2nd US Circuit Court of Appeals in New York City on Thursday evening. They hope to convince a judge that the blind collection of phone records belonging to millions of Americans is unconstitutional, and that authorities hoping to identify terrorists should only focus their efforts on those suspects.

“Courts have insisted that the government’s intrusions on privacy be precise and discriminate,” the ACLU lawyers wrote in their appeal. “The phone-records program is anything but. To pursue its limited goal of tracking the associations of a discrete number of suspected terrorists, the government has employed the most indiscriminate means possible – collecting everyone’s records.”

The ACLU argued that the NSA regularly violates millions of Americans’ protection under the First and Fourth Amendments by essentially mapping their connections with family, friends, religious, and countless other kinds of relationships. The metadata collected by the NSA does not include the content of an individual’s conversation – although it does account for the duration of a call, the time it was made, and the numbers of the sender and receiver.

“Phone records reveal personal details and relationships that most people customarily and justifiably regard as private,” the lawyers wrote in their appeal. “The government’s dragnet collection of this information invades a reasonable expectation of privacy and constitutes a search.”

That argument failed to convince US District Judge William H. Pauley III, who ruled in December that the NSA would be wrong not to use all of the powers within its grasp.

“This blunt tool only works because it collects everything,” Pauley said at the time. “The collection is broad, but the scope of counterterrorism investigations is unprecedented.”

Whether the blunt tool does in fact work is unclear. The New America Foundation, a Washington DC-based non-profit, released an analysis of 225 terrorism cases in the US earlier this year and determined that the NSA’s collection of telephone metadata “has had no discernible impact on preventing acts of terrorism.”

US District Judge Richard Leon previously ruled against the intelligence agency, asserting that the program “infringes on ‘that degree of privacy’ that the founders enshrined in the Fourth Amendment,” which prohibits unreasonable searches and seizures.

The legality, and future, of the program may eventually be put in the hands of the US Supreme Court.