Having just bashed the city's active water conservation program, let me put in a good word for mandatory watering restrictions.
I’ve never had anything good to say about command-and-control watering restrictions. Although they are much, much cheaper for the city than its active conservation program — and much more effective — they create dead-weight losses that don’t show up on the books.
There is a decent economic argument for watering schedule restrictions, though. I don’t remember anyone raising it in the comments to my many entries on this subject (although see Scooby's comment to the last entry), so I’ll lay out the case myself.