The National Security Agency programme that collects information on the phone calls of tens of millions of Americans suffered its most significant legal setback when it was ruled illegal by a federal appeals court on Thursday.
The three-judge panel ruled that the programme exposed by former NSA contractor Edward Snowden was not permitted by the Patriot Act, the sweeping counterterror bill passed by Congress in the wake of the 9/11 attacks.
The ruling comes at a politically sensitive moment for the NSA as Congress is beginning to debate whether to renew the section of the Patriot Act, which had been used to justify the bulk collection programme.