You see the problem with this so called grey market as you already have understood is that, by offering players from texas the opportunity to play at their online casino, they most likely break against the Texas state law by not having a permit or license in the first place. This is also why there is very few real money casinos available online in Texas. Now this is a completely different law, suited for companies and casino and or sports betting operators.
The Chapter 47 however mentioned that you and/or company are not allowed to offer any form of gambling within the state of Texas.
So by definition a resident within the lone star state should not be afraid police will come knocking on your door for having played at an online casino. Reading through the Texas Statuets Penal Code Chapter 47 it does not mention that it’s illegal to play on either off shore online casino or online casino outside texas state borders.