this is vague. it would be easier if we knew what he said. i do not know any laws, but my take on it is:
-using one of the '7 dirty words'
-cussing out someone directly
-borderline: saying 'FU', and i mean literally, not what it stands for. i dont let my kid curse, but she can say 'FU', but only if it is joking around
-using obscene gestures directly to someone.
-spitting on someone
i'm sure there is much more....enquiring minds want to know...