Washington: In a setback to the Obama administration, a judge Tuesday ruled that the controversial mass surveillance of phone records by US intelligence was "arbitrary" and "indiscriminate", raising a question mark on the spy programme intended to prevent terrorist attacks.
Federal District Judge Richard Leon said the National Security Agency's practice, which came to light following the leaks by fugitive whistleblower Edward Snowden, was an "arbitrary invasion" of American citizens' privacy.
The agency's collection of "metadata" including telephone numbers and times and dates of calls was exposed by ex-CIA analyst Snowden who fled the US to avoid prosecution and is now living in asylum in Russia.
In his ruling in a Washington DC federal court, Leon called the NSA's surveillance programme "indiscriminate" and an "almost Orwellian technology that enables the government to store and analyse the phone metadata of every telephone user in the United States".
The ruling came in a lawsuit brought by conservative activist Larry Klayman, a user of Verizon mobile who had challenged the NSA's collection of metadata on his behalf and that of a client.
The NSA had ordered Verizon - one of the largest phone companies in the US - to disclose to it metadata, including telephone numbers, calling card numbers and the serial numbers of phones, of millions of calls it processes in which at least one party is in the US.
The judge ruled the plaintiffs had demonstrated "a substantial likelihood of success on the merits of their Fourth Amendment claim and that they will suffer irreparable harm absent...Relief", referring to the clause in the US constitution that bars unreasonable search and seizure by the government.
He issued a preliminary injunction against the NSA surveillance programme but suspended the order to allow for an appeal by the US justice department, thus enabling the programme to continue for now.
Leon expressed scepticism of the programme's value, saying that the government could not cite a single instance in which the data actually stopped an imminent terror attack.
"I have serious doubts about the efficacy of the metadata collection programme as a means of conducting time-sensitive investigations in cases involving imminent threats of terrorism," he said.