Secession
The Constitution is silent on the issue of the secession of a state from the union. However, its predecessor document, the Articles of Confederation, stated that the United States of America "shall be perpetual." The question of whether or not individual states held the right to unilateral secession remained a difficult and divisive one until the American Civil War. In 1860 and 1861, eleven southern states seceded, but following their defeat in the American Civil War were brought back into the Union during the Reconstruction Era. The federal government never recognized the secession of any of the rebellious states. Following the Civil War, the United States Supreme Court, in Texas v. White, held that states did not have the right to secede and that any act of secession was legally void. Drawing on the Preamble to the Constitution, which states that the Constitution was intended to "form a more perfect union" and speaks of the people of the United States of America in effect as a single body politic, as well as the language of the Articles of Confederation, the Supreme Court maintained that states did not have a right to secede. However, the court's reference in the same decision to the possibility of such changes occurring "through revolution, or through consent of the States," essentially means that this decision holds that no state has a right to unilaterally decide to leave the Union.
Read more about this topic: U.S. State