I don’t know the rules but I seriously doubt the Texas State Guard is expanding it’s roles with out of state units.
http://www.txsg.state.tx.us/faq.aspx
There are several differning groups and the names get confused at times.
Texas Military forces
.. Texas State Guard
.. Texas Army National Guard
.. Texas Air National Guard
In addition there are others such as:
.. Texas State Militia .. http://www.texasstatemilitia.com/about-us.html
But as far as I know they haven’t been mobilized as of yet. That’s why I pinged
BuckeyeTexas as she has info.
I read an article I think yesterday where Texas officials said the militia were welcome but they needed to sign up with the guard.