The passage of the Patriot Act in October 2001 is by now an all-too-familiar story. The American people, already suffering from the trauma of 9/11, were pushed into outright panic by the anthrax attacks, a series of anthrax-laced mailings that killed five, injured 17 and shut down congress for the first time in modern history. The Act itself was introduced on a Tuesday and signed into law on Friday, before anyone had read let alone understood the sweeping changes it would introduce to American law.

One of those changes were amendments to a little-known and little-used FBI instrument called National Security Letters.

Find out more about how the US government keeps its opposition silent with these constitution-destroying investigative tools on this week's edition of The Eyeopener.