Looting often accompanies riots, whatever the reason for the rioting. We hail those who protected their property with firearms. Yet, there's a wrinkle in the use-of-force laws of most states in that you may not use deadly force to prevent a property crime or to merely protect property. You must know exactly what your use-of-force laws permit in the state in which you reside or where you may have to use force. The only usual exception is arson of an occupied dwelling.
During Super-Storm Sandy, a local retail business near me posted a huge sign reading, "Looters will be shot." Really? I'm in New York, a very blue state. Had the proprietor carried out his warning or advisory, he would have faced very serious felony charges and life as he knew it would come to an end.
Sorry, I don't have a sure-fire answer to prevent looting that will pass legal muster in all 50 states. But, my continued freedom is worth more than the contents of a store.
I posted in another thread, the way to stop looting is fly over head and drop job appellations, they will run away in fear.