Research on firearm purchaser licensing laws has found population level reductions in firearm-related mortality. Limited research has been conducted specifically examining the impact of these laws among adolescents and emerging adults. We obtained death data from the National Center for Health Statistics from 1990 to 2019. We generated state-year rates of homicide and suicide, stratified by firearm involvement, for decedents aged 15 to 24. We stratified by race and ethnicity (white, Black, and Hispanic) to assess for differential policy effects. We used stacked difference-in-difference and augmented synthetic control modeling to estimate law repeal or adoption. Repeal of firearm purchaser licensing laws was associated with significantly higher rates of firearm homicide and suicide among those age 15 to 24. The adoption of these laws was associated with significantly lower rates of firearm homicide and suicide among this group. These laws are a promising supply-side intervention to reduce firearm mortality among those with elevated violence vulnerability.