There is no prohibition in the United States Constitution that forbids any state from exiting the union. The Constitution of the United States actually defines the specific acts States are forbidden from committing in Article 1, Section 10. Nowhere in the remainder of the Constitution is the issue of a State leaving the Union explicitly forbidden, nor is power ceded to the federal government to prohibit one from doing so. In this silence, the Tenth Amendment to the Constitution rings loudly.
“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.”Constitution of the United States, Tenth Amendment
This deafening constitutional silence, coupled with the definitive reservation of power by the States, leaves the decision to the people of a State and to those people alone. For this, we have to look to the Texas Constitution. Article 1, Section 1 not only expressly reserves all sovereignty not granted through the United States Constitution, but it also sets the conditions upon which Texas will remain in the union.
Texas is a free and independent State, subject only to the Constitution of the United States, and the maintenance of our free institutions and the perpetuity of the Union depend upon the preservation of the right of local self-government, unimpaired to all the States.Texas Constitution, Article 1 Section 1
In the very next section of our governing document, the power to determine how Texans govern themselves is clearly declared to reside in the people of Texas alone.
All political power is inherent in the people, and all free governments are founded on their authority and instituted for their benefit. The faith of the people of Texas stands pledged to the preservation of a republican form of government, and, subject to this limitation only, they have at all times the inalienable right to alter, reform or abolish their government in such manner as they may think expedient.Texas Constitution, Article 1 Section 2