Answer: Yes, they are legally married because of the full faith and credit clause of the U.S. Constitution.
Explanation:
There is a clause in the United States constitution that states people can marry in another state and is legally binding unless there is a public policy in place in the state. If a person marries in Las Vegas and gets a marriage certificate, the marriage is valid in any state including Texas.
The requirements to marry in Las Vegas are not as restricting as some states. There is no blood test needed, no waiting period, and as long as the adults are consenting and over the age of 18 they can legally wed.