Looks like a meaningless nullity to me. Courts don't usually pass laws, even in other countries, and even if they did, there aren't really any cases where they could become binding on Texas unless via the route of federal treaties, in which case Texas wouldn't have any power to exempt itself. Also, the United States is a common law country, which means that the most obvious place this could have a meaningful impact is in the English legal traditions that the nation, and the state of Texas, take for granted. So, it would probably be more accurate to say that Texas just banned the Magna Carta than Sharia. This is more about messaging to the base, and perhaps anti-Muslim paranoia than real law, and is a great example of what happens when idiots write laws.
Also, given that this was apparently sparked by an Islamic religious tribunal set up to adjudicate divorces voluntarily between Muslims, I'm somewhat amused by the newfound zeal Christian right-wingers have found for defending the secular, civil nature of marriage. It seems to me that when the question was equality of marriage for LGBT people, that wasn't much of a concern for them.
