The National Council of Architectural Registration Boards (NCARB), a federation of all registration boards in the United States, sets national standards for architectural registration (aka Model Law). It is still up to each state to define what their own laws and regulations are regarding licensure and practice requirements, but all will base their rules to some extent on the NCARB Model Law.
NCARB manages the standardized national programs used by the state boards to determine qualifications for licensure (AXP & ARE). NCARB establishes, interprets, and enforces the AXP training requirements. They develop and administer the ARE through Prometric testing centers. They also manage the NCARB certificate program, which allows for easy reciprocal licensure in multiple states once you obtain your first architectural license.
The Texas Board of Architectural Examiners (TBAE) is based in Austin and is a member of the National Council of Architectural Registration Boards (NCARB); it regulates the licensure and practice of architecture in the state of Texas.