Provides state grant funding for up to three local governments that have demonstrated a need for services for juveniles who are alleged to have committed unlawful possession of a firearm.

Requires a Washington State Institute for Public Policy literature review of interventions for individuals alleged to have committed or adjudicated for juvenile unlawful possession of a firearm offenses with a report due December 1, 2019.

Makes the fourth offense for juvenile unlawful possession of a firearm an offense that triggers a standard range of fifteen to thirty-six weeks at a juvenile rehabilitation institution.

Requires a minimum of six months community supervision (county probation) for juveniles adjudicated for juvenile Unlawful Possession of a Firearm who are not confined in a juvenile rehabilitation institution.