According to the Constitution, who has the authority to admit new states into the Union?

The authority to admit new states into the Union is vested in Congress, as outlined in Article IV, Section 3 of the U.S. Constitution. This section grants Congress the power to create new states and to regulate their admission. This authority reflects the principle that Congress has the responsibility to oversee the governance and expansion of the United States, maintaining a unified framework for all states.

The other entities mentioned in the choices do not have the authority to admit new states. The President can influence the process and has a role in federal governance, but it is Congress that exercises the definitive power. State legislatures may have some influence in matters related to their status, but they do not have the constitutional authority to admit states. Similarly, the Supreme Court interprets laws and adjudicates disputes, but it does not have the power to create or admit states. Understanding this allocation of powers is key to grasping the federal structure established by the Constitution.