Depending on the map it can be very easy to determine who is chamming or not. Snow Valley and Kill Creek are two main examples of people sniping with chams. Also, if you yourself cham.. you can watch the people watch your movements until you appear into sight. It's a dead giveaway when your behind a rock and the opponent is, but they don't come out until you do, and they go the same direction as you. It's like a game of cat and mouse between chammers.
I've never been banned for chamming and none of the people I've become good friends with that cham on Combat Arms haven't been banned. I highly doubt you will unless you make it obvious.