Even if they voted for it and ratified it they couldn’t over turn it or legally secede from the USA.

In the 1869 case Texas v. White, the court held that individual states could not unilaterally secede from the Union and that the acts of the insurgent Texas Legislature — even if ratified by a majority of Texans — were “absolutely null.”

When Texas entered the Union, “she entered into an indissoluble relation,” Chief Justice Salmon P. Chase wrote for the court. “All the obligations of perpetual union, and all the guaranties of republican government in the Union, attached at once to the State. The act which consummated her admission into the Union was something more than a compact; it was the incorporation of a new member into the political body. And it was final. The union between Texas and the other States was as complete, as perpetual, and as indissoluble as the union between the original States. There was no place for reconsideration, or revocation, except through revolution, or through consent of the States.”

Chase added: “The ordinance of secession, adopted by the convention and ratified by a majority of the citizens of Texas, and all the acts of her legislature intended to give effect to that ordinance, were absolutely null. They were utterly without operation in law.”

Another source of confusion and misinformation over the years has been language in the 1845 annexation resolution that Texas could, in the future, choose to divide itself into “New States of convenient size not exceeding four in number, in addition to said State of Texas.” But the language of the resolution says merely Texas could be split into five new states. It says nothing of splitting apart from the United States. Only Congress has the power to admit new states to the Union, which last occurred in 1959 with the admission of Alaska and Hawaii.