Abstract: Proponents of regionalism usually blame the recognition of local autonomy, otherwise known as "home rule," for familiar metropolitan problems - housing segregation, the stark divide between rich and poor communities, environmentally destructive sprawl. They say that states have enabled municipalities to act like independent sovereigns and that selfish local policymaking has led to problematic growth in virtually every metropolitan area. Regionalists argue, therefore, that in order to stop individual municipalities from pursuing parochial ends, power must be shifted upwards - if not entirely, then substantially. But regionalists doubt this shift will occur. Why, they wonder, would local communities favor dismantling such an empowering legal structure? We offer a different view. We do not think that local governments have anything like autonomy. Even states that have formal home rule structures place significant limits on local policymaking, and greater-than-local forces exert significant pressure on local choices. It seems implausible, therefore, that local actors understand themselves to be autonomous in any meaningful way. The form of local power most cities and towns possess grants them only limited authority. It is this condition of having limited power - rather than of being autonomous - that underlies the wariness towards regionalism. This condition encourages an insular and defensive mindset that makes regionalism an unattractive risk. The parochialism that regionalists rightly wish to check, therefore, is as much a consequence of the constraints that cities and towns confront as of the powers they possess. This suggests that "defensive localism" - the defense of local power in order to preserve the status quo - rather than "local autonomy" best describes the current form of local power. We find empirical support for this alternative account in a study we recently conducted on home rule in metropolitan Boston. Our research plan was simple. We first mapped the powers that Massachusetts permits local governments to exercise. We then interviewed local officials from the 101 cities and towns located within Boston's metropolitan area. We asked two types of questions: Did the legal structure of local power in Massachusetts confer home rule in the "local autonomy" sense? And, did the local official think regionalism presented an attractive solution to the problems of their community or the region as a whole?