Offshore gambling sites are causing various issues in the United States (U.S.). Previous studies have focused on the characteristics of people who gamble on offshore sites and their motivations for doing so. This study uses the Routine Activities Theory (RAT) to understand environmental and structural factors that influence the use of offshore gambling sites. The results show that online visibility of offshore sites may predict their use among Americans who gamble. Online casino reviews provide a blacklist of unreliable online gambling sites. They can act as informal guardians, helping people to avoid offshore sites that could pose a risk.