The agency's collection of "metadata" including telephone numbers and times and dates of calls was brought to light by ex-NSA contractor Edward Snowden.
The White House dismissed the suggestion Mr Snowden receive amnesty if he stopped leaking documents.
In his ruling in a Washington DC federal court on Monday, Mr Leon called the NSA's surveillance programme "indiscriminate" and an "almost Orwellian technology that enables the government to store and analyze the phone metadata of every telephone user in the United States". 'Irreparable harm' » | Monday, December 16, 2013