User blog comment:James12708/Reapers VS. Forerunners VS. Angels from Darksiders VS. Humanity from Halo VS. Council and humanity from Mass Effect VS. Imperium of Man/@comment-50.80.96.33-20130112163411/@comment-4967682-20130123015914

The codex also says that lasers and other energy weapons are able to bypass Reaper barriers "to some extent", i.e. not entirely.