The Community-Based Gang Intervention Act establishes a new federal grant program to fund nonprofit organizations that work to reduce gang violence through community-based interventions. Eligible organizations must have a history of providing services to gang members, youth, and affected families, and the bill defines specific activities they can conduct, including street mediation, violence crisis response, mental health services, job training, and victim support. The legislation affects gang-involved youth, their families, and communities experiencing gang violence, particularly by requiring 24-hour crisis intervention services and comprehensive mental health support. The bill amends the existing Juvenile Justice and Delinquency Prevention Act of 1974 to create this new grant program and ensure participating agencies are held accountable for providing holistic, integrated services in a cost-effective manner. While the legislation does not specify funding amounts or implementation timelines in the provided text, it authorizes appropriations to support these community-based gang intervention grants subject to congressional budget approval.