If I were in that situation, I would just formulate a plan to go up the chain of command. In all forms of work/business/teaching, a chain of command is in place for situations like this. Gather your (and your line's) thoughts and present it to the Band Director. Next is the Band Boosters / Band Parents (who have a lot more pull than you realize). If that doesn't work, the Principal. No principal in his/her right mind would ever let something like this continue for long.

Have you tried talking to the local police? Make a copy of your practice schedule hand it to the nice officer and tell him what his is driving. Then when he gets busted for O.W.I/D.W.I (whatever applies for your state) everyone in the school board will take notice and that should be the end of it.