Besides procedural defenses that could be raised, there will be two main substantive legal defenses against an assault charge. First, there’s consent. If someone gives permission to another to cause bodily injury, then there cannot be assault. For example, two boxers who enter a ring for a boxing match are consenting to have the other try to cause bodily injury to the other. Second, there’s self-defense. If someone were to attack you on the street and in the process of defending yourself you hurt them, you cannot be charged with assault.