Canada geese are protected by the Migratory Bird Treaty Act (16 USC 703-711) and Illinois State Law (520 ILCS 5/2.1). People are allowed to use harassment techniques to get geese to move to another location. However, shooting at birds with a paintball gun would not fall under this category. If hit, a bird could be severely injured. I contacted the local IDNR district wildlife biologist and he suggested that it may be worth having an IDNR conservation police officer visit to assess the situation. Please e-mail me if you have more questions.