The question of whether states can legally secede has been a contentious one for centuries. While the Supreme Court declared unilateral secession unconstitutional in White (186), it is still possible for states to separate from the Union with revolution or the consent of other states. The Constitution does not provide for secession, and it does not contemplate its own destruction or the dissolution of the government. The Constitution of the United States can be amended, but it does not provide a means for its own dissolution.
This is made clear in a proposal made in the Constitutional Convention of 1787 to grant the new federal government specific power to suppress a secessionist state. James Madison, widely recognized as the Constitution's key founding father and scholar, rejected this proposal stating: “A Union of states containing such an ingredient seemed to provide its own destruction.” The guarantee of State sovereignty is enshrined in the Tenth Amendment to the Constitution, which reserves to states all rights that have not been specifically delegated to the federal government. Since the federal government was never delegated the right to force states to submit violently, secession is properly a legal right that can be exercised at any time. Thomas Jefferson made clear his distrust of an all-powerful federal government and his palpable fear that the will of the people could easily be hijacked.
The adage that “the victors of war write history” is all too true. From school history books to Ken Burns' award-winning documentary on the Civil War, Confederate states are often portrayed as traitors who were justly punished for their evil acts. However, nothing could be further from the truth, since southern states had every legal right to separate and determine their own destiny. Abraham Lincoln was wrong in declaring war against his compatriots and citizens, as it was his decision to use military force that resolved what should have been a constitutional issue.
If Texas or any other state decides to separate from the Union in the future, they would have every legal right to do so. The most likely response would be the deployment of federal troops and suppression of dissent. It's not difficult to imagine what our nation would have been like if Lincoln had followed Charles Moster's advice and allowed slavery to continue for decades, possibly into the 20th century. At least I hope so.
Let's face it, southern states had no intention of letting all their citizens determine “their own destiny”; they wanted white landowners to determine their destiny and avoid any union interference with their desire to keep African Americans in slavery. The final question of whether the federal government can militarily force a state to remain in the Union is still very much alive today, as most states have offered petitions to get out of the vehicle. If a state decides to separate from the Union, there is no provision in the Constitution that prohibits it from doing so. The closest one can get is the Tenth Amendment, which gives all powers to states that are not banned or delegated to the federal government.
Once a state tries to separate, it becomes a foreign nation and is therefore subject to all the power that the federal government has over foreign nations. This would include the power to declare war on the secessionist state and, therefore, force it to rejoin the union.