UN missions aren't always peace keeping, the first people on the scene are usually there as peace ENFORCERS, meaning that they can shoot anyone with a weapon
regardless of whether they're being shot at or not.
Just have a look at why UN forces are sent in.
To restore order.
Whether it be that people aren't getting fod (SOMALIA), the problems in East Timor or in the middle east.
They're sent in to get someone or protect something.
Hope that helps
Phantom