The boundaries of federal multidistrict litigation (MDL) are blurring, as district courts seek innovative ways to facilitate global settlements to resolve multijurisdictional, multidimensional, national mass torts. The techniques emerging from the district courts have mostly evaded appellate review and received little scholarly attention, but they raise important challenges to traditional understandings of the nature of MDL and complex litigation. This Article argues that factually similar cases proceeding in multiple court systems in mass tort disputes create a “federalism problem” for global settlements: global settlements typically benefit from oversight by a single judge, but often there is no single judge who can exercise control over all the parties who might participate in such a settlement. This Article identifies a trend emerging in MDL settlements that attempts to solve the federalism problem by extending the MDL court’s authority. In the settlement phase, some MDL judges have begun experimenting with the exercise of power over state litigants (and even individuals who made private claims but never filed suit in any court), in order to facilitate global settlements. In this situation, the “case” appears to encompass the national mass tort settlement itself. This Article concludes that the aggregative trend toward transjurisdictional settlement authority in MDL has no basis in the MDL statute. The emerging practice submerges the federalism problem into the settlement agreement without regard to the inherent limitations on the federal court’s structural power, but the federalism problem remains unsolved.