A good strategy..
There's a time and a place to nip lawlessness in the bud. A choke point, if you will. For Cobb County, it was at the bridge over the river where any rioters would have to cross an open 200 foot long two-lane span in plain sight. For New Orleans, it was BEFORE the looters could get organized and get guns (and kevlar vests) out of looted Wal Marts and gun stores.
The mayor and governor have allowed the rioters to get past the point at which they could have most efficiently stopped them. It is going to get very messy now.