Donkeys cannot sleep in bathtubs.
This law was passed in 1924 in response to a specific incident. A rancher in Kingman, AZ had a donkey who developed a habit of sleeping in an abandoned bathtub on his property. At some point, a nearby dam failed and flooded the area, whisking the donkey (in his bathtub – what a sight!) down the valley quite a ways. The townspeople expended more resources to rescue the donkey than they would have liked, and petitioned to have this law passed.