"The only reason i haven't commited murder is because there is a law against it" Is that a morale statement ?

Now this is not my personal view. But it is something i was thinking about. I live by the rules that society sets for me. But if there was no law against killing. Would it be acceptable ? For example we all know to take a life is wrong. But in certain situations; Self defence or protecting a adult/child it seems justifiable. Yet they still took a life!