Interstate Each state admitted to the Union by Congress since 1789 has entered it on an
equal footing with the original states in all respects. With the growth of
states' rights advocacy during the
antebellum period, the Supreme Court asserted, in
Lessee of Pollard v. Hagan (1845), that the Constitution mandated admission of new states on the basis of equality. With the consent of Congress, states may enter into
interstate compacts, agreements between two or more states. Compacts are frequently used to manage a shared resource, such as transportation infrastructure or water rights. Under
Article IV of the Constitution, which outlines the relationship between the states, each state is required to give
full faith and credit to the acts of each other's legislatures and courts, which is generally held to include the recognition of most contracts and criminal judgments, and before 1865, slavery status. Pursuant to the
Extradition Clause, a state must
extradite people located there who have fled charges of "treason, felony, or other crimes" in another state if the other state so demands. The full faith and credit expectation does have exceptions, some legal arrangements, such as professional licensure and marriages, may be state-specific, and until recently states have not been found by the courts to be required to honor such arrangements from other states. Such legal acts are nevertheless often recognized state-to-state according to the common practice of
comity. States are prohibited from discriminating against citizens of other states with respect to their
basic rights, under the
Privileges and Immunities Clause.
With the federal government Under Article IV, each state is guaranteed a form of government that is grounded in republican principles, such as the
consent of the governed. This guarantee has long been at the forefront of the debate about the rights of citizens vis-à-vis the government. States are also guaranteed protection from invasion, and, upon the application of the state legislature (or executive, if the legislature cannot be convened), from domestic violence. This provision was discussed during the
1967 Detroit riot but was not invoked. in the 50 states, 2005 The
Supremacy Clause (
Article VI, Clause 2) establishes that the
Constitution,
federal laws made pursuant to it, and
treaties made under its authority, constitute the supreme law of the land. It provides that
state courts are bound by the supreme law; in case of conflict between federal and state law, the federal law must be applied. Even
state constitutions are subordinate to federal law.
States' rights are understood mainly with reference to the
Tenth Amendment. The Constitution delegates some powers to the national government, and it forbids some powers to the states. The Tenth Amendment reserves all other powers to the states, or to the people. Powers of the
U.S. Congress are
enumerated in
Article I, Section 8, for example, the power to declare war. Making treaties is one power forbidden to the states, being listed among other such powers in
Article I, Section 10. Among the Article I enumerated powers of Congress is the power to regulate commerce. Since the early 20th century, the Supreme Court's interpretation of this "
Commerce Clause" has, over time, greatly expanded the scope of
federal power, at the expense of powers formerly considered purely states' matters. The
Cambridge Economic History of the United States says, "On the whole, especially after the mid-1880s, the Court construed the Commerce Clause in favor of increased federal power." In 1941, the Supreme Court in
U.S. v. Darby upheld the
Fair Labor Standards Act of 1938, holding that Congress had the power under the Commerce Clause to regulate employment conditions. In 1942, in
Wickard v. Filburn, the Court expanded federal power to regulate the economy by holding that federal authority under the commerce clause extends to activities which may appear to be local in nature but in reality effect the entire national economy and are therefore of national concern. For example, Congress can regulate railway traffic across state lines, but it may also regulate rail traffic solely within a state, based on the reality that intrastate traffic still affects interstate commerce. Through such decisions, argues law professor David F. Forte, "the Court turned the commerce power into the equivalent of a general regulatory power and undid the Framers' original structure of limited and delegated powers." Subsequently, Congress invoked the Commerce Clause to expand federal criminal legislation, as well as for social reforms such as the
Civil Rights Act of 1964. Only within the past couple of decades, through decisions in cases such as those in
U.S. v. Lopez (1995) and
U.S. v. Morrison (2000), has the Court tried to limit the Commerce Clause power of Congress. Another enumerated congressional power is its
taxing and spending power. An example of this is the system of federal aid for highways, which include the
Interstate Highway System. The system is mandated and largely funded by the federal government and serves the interests of the states. By threatening to withhold
federal highway funds, Congress has been able to pressure state legislatures to pass various laws. An example is the nationwide legal drinking age of 21, enacted by each state, brought about by the
National Minimum Drinking Age Act. Although some objected that this infringes on states' rights, the Supreme Court upheld the practice as a permissible use of the Constitution's Spending Clause in
South Dakota v. Dole . As prescribed by Article I of the Constitution, which establishes the U.S. Congress, each state is represented in the Senate (irrespective of population size) by two senators, and each is guaranteed at least one representative in the House. Both senators and representatives are chosen in
direct popular elections in the various states. Prior to 1913, senators were elected by state legislatures. There are presently 100 senators, who are elected
at-large to
staggered terms of six years, with one-third of them being chosen every two years. Representatives are elected at large or from
single-member districts to terms of two years, not staggered. The size of the House—presently 435 voting members—is set by
federal statute. Seats in the House are
distributed among the states in proportion to the most recent constitutionally mandated decennial
census. The borders of these districts are established by the states individually through a process called
redistricting, and within each state all districts are required to have approximately equal populations. Citizens in each state plus those in the
District of Columbia indirectly elect the
president and
vice president. When casting
ballots in
presidential elections they are voting for
presidential electors, who then, using procedures provided in the
12th amendment, elect the president and vice president. There were 538 electors for the most recent presidential election in
2024; the allocation of electoral votes was based on the
2010 census. Each state is entitled to a number of electors equal to the total number of representatives and senators from that state; the District of Columbia is entitled to three electors. While the Constitution does set parameters for the election of federal officials, state law, not federal, regulates most aspects of elections in the U.S., including primaries, the eligibility of voters (beyond the basic constitutional definition), the running of each state's electoral college, as well as the running of state and local elections. All elections—federal, state, and local—are administered by the individual states, and some voting rules and procedures may differ among them.
Article V of the Constitution accords states a key role in the process of amending the U.S. Constitution. Amendments may be proposed either by Congress with a
two-thirds vote in both the House and the Senate, or by a
constitutional convention called for by two-thirds of the state legislatures. To become part of the Constitution, an amendment must be ratified by either—as determined by Congress—the legislatures of three-quarters of the states or
state ratifying conventions in three-quarters of the states. The vote in each state (to either ratify or reject a proposed amendment) carries equal weight, regardless of a state's population or length of time in the Union.
With other countries U.S. states 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. The 50 U.S. 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. The federal government is responsible for
international relations, but state and local government leaders occasionally travel to other countries and form economic and cultural relationships. ==Admission into the Union==