Don't forget about the April 1, 2013, USEF rule that necessitates the usage of protective headgear by anyone mounted on the grounds at all USEF dressage competitions.
Rule DR120 states:?From the time horses are officially admitted to the competition grounds by competition management, anyone mounted on a horse at any time on the competition grounds including non-competing riders, riders on non-competing horses, and those competing in all classes and tests, including Para-Equestrian tests must wear protective headgear as defined by this rule and otherwise in compliance with GR801. Any rider violating this rule at any time must immediately be prohibited from further riding until such headgear is properly in place. Protective headgear is defined as a riding helmet which meets or exceeds ASTM (American Society for Testing and Materials)/SEI(Safety Equipment Institute) standards for equestrian use and carries the SEI tag. The harness must be secured and properly fitted.