My dissertation project seeks to understand when and how do national judges play an active and significant role in how international legal orders do or do not affect their polities. Specifically, I look at when and how British judges play a role in how European Union law through the European Court of Justice and European human rights law through the European Court of Human Rights affect the British polity. These international legal orders contain both vertical and horizontal aspects. Vertical aspects include the highest court and its judges defined by the treaty, which operates as the international, hierarchical authority on the treaty and is tasked with ensuring the compliance of the member states of the treaty. Horizontal aspects include member state courts and judges who interact with other member state courts and judges as equals voluntarily to share an understanding of the law. Britain is interesting because it may seem like a counterintuitive place to find such dynamics. Britain has a strong resistance to international authority, a deeply entrenched idea of Parliamentary Supremacy, and a dualist legal tradition where Parliament translates international law into domestic law prior to its use by the courts, which contributes to a lack of expectation of British judges engaging in international judicial activism, making Britain a hard case. In this context, we should expect that international law only matters to the extent that domestic actors are forced to incorporate it by a strong international legal order with vertical supremacy and unambiguous authority. To the contrary, my dissertation shows that British judges are quite active in many international legal orders in ways that do not merely reflect the degree of established vertical legal authority. Through dynamics that are quite autonomous from British politicians' difficult interactions with international authority, British judges play a very active role in managing and integrating international law into British politics. To see these dynamics and understand how international law has affected British politics, we must pay special attention to horizontal legal integration. Horizontal legal integration occurs when judges intentionally and selectively borrow legal concepts and precedents from other national or international jurisdictions.