The legal limit is 5.5 inches in location restricted areas. I’m assuming the knife used was no larger than a pocket knife. *if the knife was longer*, then it was illegal. But if not, he was 100% allowed to have that knife there.
Texas State Knife Laws
According to the Texas State Constitution, residents and visitors have a right to bear arms such as knives. There is no restriction on the possession of a knife. Knife-friendly statutes are in place because the state’s lawmakers seek to maintain the vibrant recreation industry, including hunting and angling.
Are folding knives legal in Texas? Yes
Are automatic/switchblades allowed? Yes
Fixed blade length: 5.5in