[JRutledge]

This would depend on the area you live and the person you are getting games from. In my experience the only contract is an email one where they ask you to work the game and you accept. If they change the circumstances then you could decide to not accept the assignments. How that is received and how that affects your career with that person might be the biggest fall out. I do not see how legally anyone can hold you to the commitment other than what standards apply to your area or policies of your association.

Peace