SOLIDARITY FEDERALISM

Studies of federalism, especially in the United States, have mostly centered on state autonomy and the vertical relationship between the states and the federal government. This Article approaches federalism from a different perspective, one that focuses on state solidarity. We explain how solidarity structures found in constitutional federations-including the United States-generate solidarity obligations, such as duties not to harm other states or their citizens. These duties give rise to principles, such as nondiscrimi-nation, that are vital to federalism. Focusing on interstate relations and relations between states and citizens of other states, we argue that affirming both solidarity and autonomy as crucial-indeed constitutive-elements of federalism enables us to better understand our federation and enriches federalism discourse in general. For example, we show that solidarity works in tandem with state autonomy to generate the traditional values of federalism, such as diversity, efficiency, experimentation, and pluralism.