Marin County Supervisors agreed last week to implement a series of amendments to a social host ordinance designed to deter underage partying that added marijuana, party buses and limousines to the prohibition and further outlined the requirements for offenders undergoing restorative justice programs. Passed in 2006, the ordinance imposes a civil fine of $750 on people responsible for gatherings where alcohol or drugs are consumed by minors or are in their possession. (Supervisors previously the ordinance in early 2016 by adding controlled substances to the prohibition.) The new amendments expand the language by listing marijuana alongside alcohol and controlled substances, and add party buses and limousines to the list of gatherings where loud and unruly parties are prohibited. They also mandate graduation from a restorative justice program for offenders under age 21, and six to 20 hours’ attendance at a restorative justice program for adult offenders (in addition to the fine). Since 2006, the Marin County Sheriff’s Office has issued nearly 80 citations; according to Jack Grovi, assistant county counsel, about 10 percent were in West Marin. “Substance abuse is a chronic and consistent problem for us in this county,” Dr. Matt Willis, the county’s public health officer, told supervisors on Tuesday. “For seven years in a row, the Robert Wood Johnson Foundation has found us to have an extraordinarily high burden of substance use compared to other counties.” Madeline Hope, a member of the West Marin Coalition for Healthy Kids and director of the Tomales Bay Youth Center, told supervisors that the county’s Health and Human Services and Office of Education have made the social host ordinance a priority in recent years. “That has really been a highlight for me, to see the different departments getting in step with one another,” she said. Josh Rowe, a high school student at San Domenico School and former resident of PRS who sits on the Marin County Youth Commission, told the board about his experience as a teenager in Marin. “Living here has allowed me to witness the issue of underage drinking first-hand—especially in my old community of West Marin,” he said. As part of the youth commission, Mr. Rowe worked alongside county groups to amend the ordinance. He spoke in favor of bolstering the restorative justice program mandates in particular: “They allow the youth offender a safe space where they can discuss what they did wrong and truly comprehend the impact their action had on the community.”