Cities in most states enjoy broad “home rule” authority—that is, the presumptive power to regulate a wide range of subjects. In many of these states, however, home rule comes with a catch: cities are prevented from interfering with “private law.” This Article argues that the “private law exception,” as this doctrine is known, is an anachronistic relic of early twentieth century legal thought that ought to be retired outright. This Article explains how a subject-based view of the private law exception, which prevents cities from passing ordinances affecting subjects like contracts, property, and torts, is largely unenforced today. The more relevant and potent form of the private law exception, by contrast, prohibits cities from enacting ordinances that create private causes of action, thereby requiring local ordinances to be enforced exclusively by public means. This constraint limits both the effectiveness of local policy choices as well as their social impact. As this Article will show, the primary justification for the contemporary private law exception—protecting the interests of the state courts—is not sufficiently compelling to outweigh the costs to local policy experimentation that the exception imposes.