For as long as I can remember, Texas secession has always been a joke of sorts thrown about when Texans got tired of Washington. Growing up I remember seeing what was mostly pick up trucks with bumper stickers reading 'SECEDE'. Of course you could chalk that up to me having lived in Rockwall, the last bit of civilization east of Dallas and a decidedly I <3 Texas locale. However, Texans in general seem to all have the same idea: We don't need Washington.
But legally can Texas secede? No. According to the 1845 Texas Annexation Agreement, Texas can if it chooses split itself up into 5 states, but who would want that? In the 1869 case of Texas v White, the Supreme Court decision held that no state had the right to secede from the Union. So... there goes that theory.