When federalist nations are signatories to international economic agreements, potential problems arise because of the inherent conflicts between federal law and legitimate state interests. This paper presents a conceptual framework for analyzing problems surrounding negotiation, ratification, and implementation of international agreements when federations are signatories. The economic model isolates three factors (the variance of state net benefits under an agreement, individual states' opportunity costs associated with the agreement, and state-supported opportunism) as cost-increasing impediments to the successful institution of international economic agreements and highlights opportunism containment as fundamental to credible commitments in international agreements.