This presentation is a case study of challenges to investigating sex trafficking created by decriminalized prostitution. For 29 years (from 1980 to 2009) in Rhode Island, engaging in prostitution was not prohibited or regulated. Commercial sex acts were private and beyond the interest of the state. Lack of laws or regulations of prostitution created a permissive legal, economic, and cultural environment for the growth of prostitution businesses. Local police were impeded from investigating alleged sex trafficking because police had no legal cause to investigate private activities. In interviews, law enforcement officials repeatedly stated that they did not have the laws they needed to conduct investigations. Police tried using health, fire, and building codes to find a legal path to investigate the brothels, but attorneys defending the brothels were aggressive in countering police efforts. Because local and state police were hindered from investigating prostitution, they could not partner with federal law enforcement agencies in national initiatives to investigate sex trafficking of minors. Also, federal laws, such as Transportation for Illegal Sexual Activity and Related Crimes, could not be used because prostitution was not an illegal activity. Federal investigations of international smuggling, transportation, and sex trafficking initiated in other states linked brothels in Rhode Island to international sex trafficking networks. Decriminalized prostitution and lack of investigations into sex trafficking made Rhode Island a destination for sex traffickers. After decriminalized prostitution had ended, traffickers who were arrested said they brought victims to Rhode Island because prostitution was legal. The Rhode Island experience with decriminalized prostitution and its hindrance of investigation of sex trafficking serves as a cautionary note for current advocacy for decriminalized prostitution.