In 2 recent cases-with important implications for public health practitioners, courts, and researchers-the US Supreme Court changed the landscape for judging the constitutionality of firearm laws under the Constitution's Second Amendment. In District of Columbia v Heller (2008), the court determined for the first time that the Second Amendment grants individuals a personal right to possess handguns in their home. In McDonald v City of Chicago (2010), the court concluded that this right affects the powers of state and local governments. The court identified broad categories of gun laws-other than handgun bans-that remain presumptively valid but did not provide a standard to judge their constitutionality. We discuss ways that researchers can assist decision makers.