The Resolution of Annexation, Dated March 1, 1845, had no such language. What it gave Texas the right to do is: "Third -- New States of convenient size not exceeding four in number, in addition to said State of Texas and having sufficient population, may, hereafter by the consent of said State, be formed out of the territory thereof, which shall be entitled to admission under the provisions of the Federal Constitution; and such states as may be formed out of the territory lying south of thirty-six degrees thirty minutes north latitude, commonly known as the Missouri Compromise Line, shall be admitted into the Union, with or without slavery, as the people of each State, asking admission shall desire; and in such State or States as shall be formed out of said territory, north of said Missouri Compromise Line, slavery, or involuntary servitude (except for crime) shall be prohibited."
In other words - it gave Texas the right to divide into 5 states.
But it does not have the legal right to secede. It would have to secede and possibly be a rebel state, and face the possibilities of a civil war with the Federal government.
Secession was and always will be extrajudicial. The colonies had no right to leave England legally. I would encourage people to read the declaration of independence it lays out the natural human rights of self governance in language the common man can understand. Texas citizens have the natural right to choose self governance and the consent of the governed. If the majority of Texans vote for independence we have the right to say so by God and if the feds deny that right then it’s tyranny and fighting tyranny is obedience to God it’s our duty to fight tyranny with arms to the death if need be. Once independence has been declared the consent to be governed by the existing government is null and voided. People get too wrapped up in the “legality” of secession that’s a logical fallacy secession is always outside the existing laws by it’s very nature. Ears are fought for independence for a reason , Texas has won three times already once against Spain when it was then part of the newly independent Mexico then from Mexico and again as part of the USA when Mexico tried again in the Mexican American way to annex Texas. We would have to fight the Fed’s make no.mistakes about it but it’s a fight worth killing for. Patton famously said wars are not won by dying for your country it’s making the other poor sap die for his.
No - Texas does not have a right to secession. You are historically misinformed (and yes, I am from Texas).
Every state has a right to secession.