State and local regulations--laws, ordinances, policies--form the framework of any effort to reduce underage drinking. The right regulations, well crafted, can minimize the opportunities for young people to use alcohol and maximize opportunities for effective and efficient enforcement. The absence of an important regulation, or loopholes in the regulation, can put youth in harm's way and frustrate enforcement efforts. This guide provides information on the regulations that are most important in reducing youth access to alcohol and underage drinking. It spells out the best practices for establishing appropriate laws and regulations and suggests priorities for regulatory and enforcement efforts. It also discusses some of the implementation issues that will be crucial for the successful adoption and implementation of these regulatory strategies. The guide divides regulations into the following three categories, depending on which aspect of youth access or use they address: (1) "Commercial availability," which focuses on the practices of alcohol retailers such as liquor or grocery stores and bars; (2) "Social/public availability," which focuses on noncommercial sources of alcohol (such as older friends) and noncommercial venues where young people consume alcohol (such as parties); and (3) "Youth possession," which focuses on deterring young people from attempting to purchase or consume alcohol. (Contains 4 footnotes.)