Trial by jury, self incrimination, double jeooardy, and search warrants.
What you basically need to know is that the contras were right-wing and that they opposed the left-wing government.
The left-wing governments were generally not seen as desired during the cold war because they could strengthen the communists, which were competing with the US.
So the US hoped that the contras would weaken or even replace the left-wing government.
