my understanding is states determine zoning laws, which municipalities apply. For example, MA state zoning law determines that cities and towns need a supermajority vote to change their zoning plan, so it's usually politically infeasible for cities and towns to change their zoning except as maybe the occasional once-in-a-generation thing. As a result, most development around here happens through zoning variances, which have to be approved by the local zoning board and are subject to all sorts of hearings and generally get very held up compared to by-right zoning.
