If your definition of "conspire" includes "taking unilateral action against innocent citizens with no basis in suspected criminal activity", then /u/JumpingJimFarmer's answer on Japanese internment during WWII is a good place to start.

This thread by u/Snapshot52 gives a great insight into the wider FBI treatment of the American Indian Movement (AIM)and specifically how the FBI conspired to convict Leonard Peltier (an AIM member) of two murders on extremely flimsy evidence.