The use of various controlled and illegal substances, especially by young adults, has been a cause of much concern among policymakers, law enforcement officials, educators, and parents. State-level legalization of recreational marijuana in the United States raised concerns about potential adverse impacts on campus drug use and drug law violations. This paper combines data from three sources for 2001-02 to 2023-24, including college campus drug law violations that are collected under the Clery Act of 1990. We find that state legalization of recreational marijuana substantially reduced the arrests and disciplinary incidents for drug law violations.