(When you find a cat barf, it's likely not the main barf but one in a series of afterbarfs, each one smaller than the last. It's a matter of following the trail back to the main barf, otherwise known as the Motherglort)
Some places have done this for years; the city I'm in considers cats and dogs (well, all animals except fish and birds, for some reason) to be identical as far as licensing, being "at large", requirement for leashes, etc.
Between the risk to cats by running free outdoors, and the risk cats present to other animals, peoples' property, etc., there's no reason cats should be allowed to roam freely.