ISB, like all secret police and intelligence agencies, sometimes finds itself needing arm breakers, neck twisters and shooters. When someone needs to get hurt, instead of getting stormtroopers, the ISB turns to it's Enforcement branch. Mostly graduates of COMPForce, the full Agents of this branch of the ISB are skilled and dangerous warriors. They are authorized to use whatever force is needed to accomplish thier mission.
If they find themselves needing extra firepower, Field Agents are allowed to hire mercenaries and hoods for extra muscle. (It should be noted that this is only approved of by the after-action review board if the local Govenor would not release Stormtrooper/COMPForces, Stormtroopers/COMPForces where unavailable, or Imperial deniability was required. In reality, it almost always is.) This willingness to use non-COMPNOR members, much less the non-humans used by ISB-E, has led to a great deal of tension with the branches of the ISB.