The governor is relying on chapter 418 of the Texas Government Code, which governs disasters. Under section 418.012, the governor, during a disaster, “may issue executive orders, proclamations, and regulations” which “have the force and effect of law.” Under 418.173, the governor may make violation of an “emergency management plan” or an order under the plan an offense with a penalty up to 180 days in jail and a $1,000 fine, which would be a misdemeanor.
So the answer according to the governor is the mask order is law and violation of it is a misdemeanor. However, I question whether the order is within the scope of the governor’s powers under Chapter 418 and whether the mask order is an “emergency management plan.” I also question its constitutionality: for one, I think it violates due process because it is unconstitutionally vague.