Because it will ultimately be overturned as unconstitutional. Texas has tried several times to enforce border law, and even had programs in the past (along with Arizona) that allowed the Border Patrol to deputize and train certain state LEOs.

I love the idea, but until a law like this comes from CONgress a leftist Federal judge will stop it every time. For that matter the infamous Hawaiian judge may even make another appearance. It's infuriating.