break a/the law
To do something that is illegal. If you shoplift, you are breaking the law, period. The statutes are different in different places so sometimes you can break a law without even knowing it!
break a law
and break the lawto fail to obey a law; to act contrary to a law. Lisa broke the law when she drove the wrong way on a one-way street. If you never break the law, you will never get arrested.