The United States and Europe share constitutive commitments to multilevel governance in which subunits have legal autonomy and participate in shaping meta-norms. Yet subunits’ authority is limited because they share a legal-political identity that makes deviation from certain foundational norms illicit. This chapter explores mediating institutions that craft accommodations by allocating authority to respect but to cabin differences. Translocal organizations of government actors, spawned by federalist regimes and crisscrossing the boundaries of individual subunits, do not map neatly onto the territory of subdivisions. They regularly appear in apex courts, asked to rule on conflicts about issues such as immigration and violence against vulnerable persons. Those interactions make plain that jurisdictional essentialism, linking domains of law to particular levels of government, misses how legal rules are made through interactions in which the subunits’ or larger entities’ interests are not fixed ex ante. The development of doctrines such as the “margin of appreciation” of the European Court of Human Rights exemplifies efforts to accommodate differences while building in opportunities for reconsideration that enable revisiting prior rulings, even as that doctrine permits the underenforcement of constitutive rights or overrides subunits’ claims in particular cases.