Why was Texas constitution of 1866 rejected by the union?

The Texas Constitution of 1866 was rejected by the Union primarily because it did not fully embrace the principles of the Reconstruction era, particularly regarding civil rights and the status of formerly enslaved individuals. The document failed to provide adequate protections for the rights of freedmen and did not repudiate secession or the debts incurred by the Confederacy. As a result, Congress deemed it insufficient for re-admittance into the Union, leading to further military oversight and the implementation of more stringent Reconstruction measures.