Megan's Law requires government notice to communities of resident sex offenders believed to possess a high risk of recidivism. The community receives the offender's name, address, offense, place of employment or schooling, and license plate number, along with a recent photograph and a physical description. The community is also admonished against vigilantism and is warned that crimes against the offender will be prosecuted. The laudatory objective of Megan's Law is community self-defense, and the law is constitutionally sound and necessary. Critics, however, assail Megan's Law as an invasion of privacy, as repeat punishment for persons who have already served their sentences, as generating vigilante acts, as unfairly stigmatizing former convicts in need of support to get their lives back in order, and as ignoring the causes of sex offenses. The rationality of sex offender laws is discussed.