In a world in which barriers to trade at all levels - international and internal - are mostly a by-product of the implementation by governments of different regulatory policies to deal with domestic or local problems, the mechanisms that are set in motion by the operation of competition among the governments inhabiting the different jurisdictional tiers of federal countries lead to outcomes that are different from those generated by the 'agreed-upon' rules that govern the relations of national governments with each other in matters of international trade. A model is used to compare two ways of dealing with the external damages that are consequent on the pursuit of beneficial domestic regulatory policies. It assumes that at the international level the methods used can be synthesized by what is known as the least-restrictive means principle, while in the context of competitive federalism the methods lead to what can be called a proper balancing of benefits and costs of domestic policies, including the spillover costs inflicted on others. With the help of this model, the paper shows that one or the other of the two sets of methods could be more restrictive, depending on the magnitude of spillovers and the relation between the instrument used and the achievement of the domestic objective. It includes also a discussion of the case of the European Union, which falls between these two polar extremes.