# abstract
Policymakers are constantly faced with the complex task of managing novel challenges. At times, these challenges result from new technologies: Consider fights over allocating air rights for drones or decisions about how to share scarce vaccines in a pandemic. Other times the resources are old, but the challenges are new, such as how to fairly allocate water in times of unprecedented drought or previously undesirable rare earth minerals that are in demand for modern manufacturing and energy production. Often, instead of carefully tailoring a regime to the new resource, decisionmakers simply rely on mechanisms they are familiar with. When jurisdictions borrow from each other, scholars call this a legal transplantas when one state copies another states innovations or when the federal government learns from the laboratories of democracy. This Article unveils a new dimension of legal transplants: transplants across subject areas. By transplants across subject areas, this article refers to instances when a jurisdiction looks for doctrines in other legal areas, often within its own legal system, when regulating a new resource or addressing a new challenge. This Article makes three key contributions. First, it identifies a new type of transplantbetween subject matters within a jurisdiction. Second, it analyzes the reasons for internal, cross-subject legal transplants and the criteria for selecting which subject areas to copy from. Third, the Article brings the legal transplants literature to bear, specifically, on natural resource law. It explores two cases, groundwater and wind energy, where policymakers and courts have borrowed from other resource schemes, often ignoring the scientific and social differences between these natural resources. Other areas of law, such as the incorporation of contract doctrines in landlord-tenant relations, are also described to show the explanatory power of the natural transplant framework. This conceptual framework is then applied to new mineral developments in space and the deep sea. Cross-subject transplants may be more prevalent than previously appreciated, and understanding them will pave the way to analyze the regulation of new developments in natural resources, infrastructure, and beyond.