Ever since the modern revival of Alien Tort Statue (ATS) litigation in 1980, Democratic administrations have favored adjudication under the statute while Republican administrations have been against it. But why would this be the case? After all, the received wisdom assumes that presidents (from either party) are empire builders who prefer to shape international law and foreign policy without any meddling from the courts. This Essay advances a partisan entrenchment logic to explain the variance in support of ATS adjudication across different administrations. Under this logic, presidents and judges are political actors whose partisan preferences regarding substantive international law will sometimes trump their institutional or interpretive empire-building objectives. Thus, presidents who are sympathetic to the ideological goals of a specific international law norm may be willing to relinquish interpretive authority to courts in order to entrench the norm in a way that binds their successors and other domestic political actors. Conversely, judges who are unsympathetic to the policy goals of an international law norm may be willing to relinquish interpretive authority to the President (or the political branches) in order to prevent legal entrenchment. These divergent approaches toward ATS adjudication have been shaped by the preferences of interest groups aligned with the Republican and Democratic parties. The Article concludes by examining the conflicting litigation positions of lawyers from the Obama and Bush Administrations over the scope of the ATS in the Supreme Court’s recent decision of Kiobel v. Royal Dutch Shell Petroleum.