The UN "peacekeepers" have had some pretty sordid track records of course, and there are cases where they had guns. But no bullets.
Anything will be better than the current ISIS regime in vast areas of Iraq and Syria. Recently, there have been a lot of scandals involving the UN peacekeepers (esp. in Congo and Haiti), but still they will do a better job than the ISIS and the Iraqi army. But patrolling such a huge area will require tens of thousands of soldiers.