Can Texas Actually Leave the union?
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.
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.