I believe that fits with the intent of the U.S. Constitution. Those who wished to join the Union could do so if those already in it consented. And this nation was founded on the concept that when a government breaks faith with the people and oppresses them against their will, that the people are justified in dissolving or removing themselves from that government.
Our Declaration of Independence from England started with these famous words:
When, in the course of human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the laws of nature and of nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation.
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable rights, that among these are life, liberty and the pursuit of happiness. That to secure these rights, governments are instituted among men, deriving their just powers from the consent of the governed. That whenever any form of government becomes destructive to these ends, it is the right of the people to alter or to abolish it, and to institute new government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their safety and happiness. . .
The opening statement was followed with acknowledgment that a people should not withdraw from a government without just and extreme cause. And then it went on to list the grievances the Colonists had with King George that provided the justification for dismissing the English government.
Certainly Texas could compile a long list of grievances of how the federal government has abused, misused, misapplied, and mischaracterized the letter and law of the Constitution. If they left, I want New Mexico to go with them.
The difficulty comes in the many many major federal installations in Texas not the least of which are NASA, 25 military installations and bases, et al that belong to us all. What could we do about that?