Section 3 of the 14th Amendment:
No Person shall be a Senator or Representative in Congress, or elector of President and Vice-President, or hold any office, civil or military, under the United States, or under any State, who, having previously taken an oath, as a member of Congress, or as an officer of the United States, or as a member of any State legislature, or as an executive or judicial officer of any State, to support the Constitution of the United States, shall have engaged in insurrection or rebellion against the same, or given aid or comfort to the enemies thereof. But Congress may by a vote of two-thirds of each House, remove such disability.
On Tuesday, Rep. Kyle Biedermann (R-Fredericksburg) said that he is committed to authoring legislation in the 2021 legislative session that will give Texans a vote to allow the state to secede from the U.S.
"The federal government is out of control and does not represent the values of Texans," he wrote on Facebook. "That is why I am committing to file legislation this session that will allow a referendum to give Texans a vote for the State of Texas to reassert its status as an independent nation."
Oyez describes Texas v. White:
In a 5-to-3 decision, the Court held that Texas did indeed have the right to bring suit. The Court held that Texas had remained a state, despite joining the Confederate States of America and its being under military rule at the time of the decision. The Court further 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." Even during the period of rebellion, however, the Court found that Texas continued to be a state.