Mage duels are neither common nor legal, they tend to be somewhat destructive and cause extreme collateral damage. Mages who wish to duel can get special permits for non-lethal dueling only which does not cause collateral damage to living creatures or inanimate objects. There are certain rituals involved in dueling (in fact the act of initiating a duel is much like casting a spell except that it requires more than one spellcaster) which must be observed by the challenger and his opponent, and all participants must have a dueling wand.
Daaaamn! Wow, impressive battle scene. Great characters, strong drama and I really like the interesting and complex layout of the scene too. Great job!