Private Army
More and more the USA relies on civilians to do what it finds reproachable or controversial, and as well to evade the strict controls imposed by law. Colombia is a prime example of this:
Big companies such as DynCorp, in charge of piloting planes that spray coca crops, and Northrop Grumman's California Microwave Systems (CMS), which operates counternarcotics missions, did not release the number of employees involved in their operations. But the report counts at least 190 contractors employed by "Plan Colombia," a US-backed antinarcotics and antiterrorism program, and estimates the risk to most of their lives as "low."
The greatest danger is for the civilian population, as these experts will often escalate the conflict, and they do not answer to the Colombian civilian government, but the USA DoD. Not completely unaccountable, but not restricted either.