Remember the Ammon Bundy incident and trial? This was the case where a group of right-wing tax protesters took over a chunk of Federal land in Oregon. A big part of their subsequent acquittal was the reveal that nine of the occupiers were actually FBI informants.

Of course, Bundy went on to do other crazy stunts later on. But given the information available to the jury at the time, they decided that the government had gone too far in the Oregon case.