Dog people, rejoice: The city's off-leash rules are finally being codified into ironclad law. Come May 1, most New York City parks will officially roll out the welcome mat for your unleashed beast from 9 p.m. to 9 a.m., the so-called "courtesy hours." ("Get-mauled-in-the-dark hours" doesn't have quite the same ring.) As tends to be the case with even the slightest adjustments to our city ordinances, this one is a result of a protracted and vicious court battle. Last year, a Queens civic group sued the city to stop the off-leash practice altogether; after the judge and the Board of Health came out on the dog-lover side, the city put the law on the books instead. With new liberties come new restrictions, though: Be ready to show the mutt's proof of license and rabies-vaccination papers at any time. Or get a cat.