This is a very silly idea. Arming guards will may deter minor looters of opportunity, but is more likely to result in death. Most of those scavenging around on archaeological sites are the poor and desperate who have no other options - they dig items up or die of starvation. And no artefact is worth a life, whether of a guard, an archaeologist or a robber. I say that as someone who design a project where too many men lost their lives, and which I still have nightmares about. Improperly trained men with guns are no obstacle to professional looters. It's a loose-loose proposal.