Written in the Constitution I believe. In 1863, Lincoln defined certain requirements in order for states to regain their constitutional protections, as defined in Article IV (Proclamation of Amnesty and Reconstruction, December 8, 1863). Specifically, for any state, which was part of the Confederacy, to have its government recognized, and in order for it to be protected from foreign invasion or domestic violence, at least ten percent of its eligible voters had to swear an oath. So if the contract is broken then Yes.
Texas did challenge the election fraud and if 70% of actual US voters voted Trump then 10% seems achievable.
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