People say Texas can't legally secede. Is that true?

No. The people who say it cannot be done are repeating a talking point, not citing a law. There is no clause in the U.S. Constitution that forbids a state from leaving, and the single court case everyone falls back on does not say what they think it says.

Start with the document itself

If leaving were illegal, there would be a line in the Constitution that says so. There is not. Article I, Section 10 is the place the Framers listed what states cannot do. They were thorough. States cannot make treaties, coin money, keep troops in peacetime, or tax imports without the consent of Congress. That list is precise, and a state leaving the union is nowhere on it. The Framers knew how to forbid a thing. They forbade many things. They did not forbid this.

Silence is not a loophole. In this system, silence is the answer

The Constitution is a list of powers the states handed to the federal government. Whatever was not handed over stays with the states and the people. The Tenth Amendment says it plainly: the powers not delegated to Washington "are reserved to the States respectively, or to the people." There is no delegated power to stop a state from leaving, and no delegated power to hold a state by force. So the power was never given away. It stayed home. Reaching for a power the Constitution never granted is not constitutional law. It is just power.

The whole case against you rests on one 1869 opinion

Press a skeptic and you always arrive at the same place: Texas v. White, decided in 1869. Take that one case away and the opposition has no law left. So it is worth knowing what that case actually was. It was a lawsuit about bonds. Texas had received $5 million in U.S. bonds under the Compromise of 1850, some were sold during the war, and the Reconstruction government sued to get them back. The only question the Court needed to answer was whether Texas could bring the suit at all. Bonds and standing. That was the case.

The famous line was a flourish, not a holding

To decide a bond dispute, Chief Justice Salmon P. Chase reached far past it and announced that the Constitution had built "an indestructible Union, composed of indestructible States." That sentence is quoted to this day as if it were the law of the land. It was not necessary to decide who owned the bonds, which makes it dictum, a comment, not a binding holding. A holding is the narrowest ground a court needs to settle the fight in front of it. Everything past that is commentary, however grand it sounds. And here is the part the talking point skips: sixteen years later, in Morgan v. United States (1885), the Supreme Court overruled the actual bond rule that Texas v. White was built to produce. The one piece of that case that was a real holding did not survive. The sweeping line about a permanent union did, not because any court ever tested it, but because the question has never been put squarely to the Court again.

The opinion even leaves the door open itself

Read Chase's own words. He wrote that once in the union there was "no place for reconsideration or revocation, except through revolution or through consent of the States." Stop on that last phrase. The very opinion used to prove Texas can never leave concedes that the union can be dissolved by the consent of the states. The case that is supposed to lock the door describes a key sitting in the lock.

The world's courts have moved the other way

While American politicians treat 1869 as the final word, the rest of the legal world kept thinking. In 2010 the International Court of Justice examined whether a people may declare independence and held that "general international law contains no applicable prohibition of declarations of independence." The Supreme Court of Canada, looking at Quebec in 1998, held that a clear majority on a clear question creates a binding duty on the other side to sit down and negotiate. The legal current is running toward the right of a people to decide, not away from it.

This was never the courts' question in the first place

Whether a people may govern themselves is a political question. It belongs to the people, not to nine appointees in Washington. The federal government's own conduct admits as much. It argued for the right of declaration in the Kosovo proceeding and signed treaties pledging to respect self-determination. The legal smoke clears to reveal a political choice that Texans have simply never been allowed to make at the ballot box.

The bottom line

There is no law that forbids Texas independence. There is one old opinion, built on a bond case, undercut by a later ruling, and contradicted by its own author. The reason there has been no vote is not constitutional. It is political. And political problems have political solutions.