Halopedia suggests that Enforcers only appear when a Flood infestation gets too large, explaining their abscence in Halo CE. This argument however, got flung right outside the window when the Flood unleashed the biggest fuckstorm in recorded history on the Ark and no Enforcers showed up. Halopedia later claimed that the Forerunners didn't expect Ebola on the Ark, thereby shooting themselves in their (Halopedian) foot after writing an elaborate article about the Forerunners and their superior technology. Bah. if you want to kill one you shoot of its arms