While each state government within the United States holds legal and administrative jurisdiction within its bounds, they are not sovereign in the Westphalian sense in international law which says that each State has sovereignty over its territory and domestic affairs, to the exclusion of all external powers, on the principle of non-interference in another State's domestic affairs, and that each State (no matter how large or small) is equal in international law. Additionally, the member states of the United States do not possess international legal sovereignty, meaning that they are not recognized by other sovereign States such as, for example, France, Germany or the United Kingdom, nor do they possess full interdependence sovereignty (a term popularized by international relations professor Stephen D. Krasner), meaning that they cannot control movement of persons across state borders. The idea of "dual sovereignty" or "separate sovereigns" is derived from the 10th Amendment to the Constitution, which states that "the powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people." Structured in accordance with state law (including state constitutions and state statutes), state governments share the same structural model as the federal system, with three branches of government—executive, legislative, and judicial.
In the majority of states (26), the state legislature is simply called "Legislature." Another 19 states call their legislature "General Assembly". Two states (Oregon and North Dakota) use the term "Legislative Assembly", while another two (Massachusetts and New Hampshire) use the term "General Court".
In the 49 bicameral legislatures, the upper house is called the "Senate".
Until 1964, state senators were generally elected from districts that were not necessarily equal in population. In some cases state senate districts were based partly on county lines; in the vast majority of states the senate districts provided proportionately greater representation to rural areas. However, in the 1964 decision Reynolds v. Sims, the U.S. Supreme Court ruled that, unlike the United States Senate, state senates must be elected from districts of approximately equal population.
In 40 of the 49 bicameral state legislatures, the lower house is called the "House of Representatives". The name "House of Delegates" is used in Maryland, Virginia, and West Virginia. California and Wisconsin call their lower house the "State Assembly", while Nevada and New York simply call the lower house the "Assembly". New Jersey calls its lower house the "General Assembly".