As far as I know these are actually really laws, although I'm assuming they aren't enforced! *lol*
In Alabama, it is an offense to open an umbrella on the street, since it might spook horses.
In Arizona, you can get arrested if you try riding your horse up the steps of the county court house.
In California, you are breaking the law if you pile horse manure more than six feet high on a street corner.
In Indiana and New Jersey, it is against the law for a car to pass a horse and carriage on the street.
In Iowa it's illegal for horses to eat fire hydrants.
In Kansas, all cars entering town must sound their horn to warn horse riders of their arrival.
In Forest City, North Carolina, you are required to stop at the outskirts of town and call City Hall before entering, to allow the townsfolk to go outside and hold their horses while you drive through town.
In Pennsylvania, if a driver sees a horse-drawn carriage coming toward him, he must pull over, cover his car with a blanket so as not to frighten the horses, and allow them to pass.
In South Carolina drivers of automobiles must stop 100 yards from an intersection and fire a shot into the air to warn horse traffic of their approach.
In Texas, while it's against the law for anyone to drive a horse and buggy through the town square, it's perfectly acceptable to ride your horse into the saloon!
In Washington State it's illegal for any person to ride an ugly horse.
In LaCrosse, Wisconsin, it's illegal to tie your horse up along Third Street (an obvious attempt to prevent riding under the influence, since Third Street was the location of a number of saloons).