There are already LOOOOTS of places in all parts of the world that have laws regarding public profanity, including where I live. Said laws are practically never enforced.
A few years ago, I used to manage a gas station. One day there was a cop in the store, as well as an older guy who looked like he was a construction worker. I can't remember why, but at one point the older guy starts cussing up a storm at something. Just as he stopped to get a breath of air, the cop interrupted and said "You done?" The older guy replied "why the .... do you care?", to which the cop replied "It's technically against the law to swear in public."
In response to that, the older fellow puffed up his chest, got right up in the cop's face and said "well, aren't you on a ....in' power trip!"
The cop responded by simply removing his shades, Horatio-style, looked him square in the eyes and said "keep going."
After about five seconds of staring each other down, the one guy moved back a bit, then stormed out of the store.
I remember it like it was yesterday, cause it was *really* entertaining to watch.