Before Megan's Law, the federal Jacob Wetterling Act of 1994 required each state to create a registry for sexual offenders and certain other offenses against children.

[4][3] After the high-profile rape and murder of seven-year-old Megan Kanka in Hamilton Township, Mercer County, New Jersey by Jesse Timmendequas, a sex offender with two previous convictions of sex crimes against small children living across the street from Megan, her parents Richard and Maureen Kanka worked to change the law by demanding mandatory community notification of sex offenders, arguing that the registration required under the Jacob Wetterling Act was not a sufficient protection measure.

[3] The New Jersey law became model for federal legislation, introduced in the House of Representatives by Congressman Dick Zimmer.

[6] On May 17, 1996, President Bill Clinton signed federal Megan's Law, an amendment to the Jacob Wetterling Act, that set the guidelines for the state statutes, requiring states to notify the public, although officials could decide how much public notification is necessary, based on the level of danger posed by an offender.

[8][9] International Megan's Law requires the notification to foreign governments when a citizen of the United States who is registered as a sex offender for sexual offense involving a minor is going to be traveling to their country.

[16] Majority of research results do not find statistically significant shift in sexual offense trends following the implementation of sex offender registration and notification (SORN) regimes.

Treatment professionals such as ATSA criticize the lack of evidence of the laws' effectiveness, the automatic inclusion of offenders on the registry without determining the risk of reoffense (by applying scientifically validated risk assessment tools), the scientifically unsupported popular belief in high recidivism, and the counter-effectiveness of the laws, which can actually undermine, rather than improve public safety by exacerbating factors (e.g. unemployment, instability) that may lead to recidivism.

[30][31] In addition, civil rights and reformist organizations highlight the adverse collateral effects on the family members of registrants, and question the fairness of the registries as indefinite punishment, and when applied to certain offender groups, such as juveniles and young adults engaging in consensual acts.