Traumatic Brain Injury (TBI) is among the most prevalent and least-understood injuries affecting athletes at all levels. A growing body of literature on the effects of TBI spurred 49 states and the District of Columbia to pass some type of law attempting to address pre-collegiate athlete TBI, and in particular multiple successive TBI. This study is the first attempting to estimate the causal effects of this set of TBI laws on high school sports participation. Using data from the National Federation of High Schools, I examine the effects of several effective components of these laws on a wide range of sports with different levels of physical contact. My results fail to find any effect of these laws on sports participation that are statistically distinguishable from zero among the most high-risk sports when grouped, but does find some significant effects of these laws on individual sports as well as positive participation effects on sports with an intermediate level of TBI risk, suggesting possible substitution effects of intermediate risk sports participation for high risk sports.