The United Nations Office on Drugs and Crime (UNODC) is aware of the fact that law enforcement measures alone cannot prevent the smuggling of migrants. If they are not part of a holistic approach, increased border controls may simply have the result of diverting migrant smuggling routes and of increasing the demand for more risky services. Where migrants are simply returned to their countries of nationality or residence without consideration for the underlying root causes that made them migrate, they may simply attempt to migrate again, perhaps under more dangerous conditions. There are important push-and-pull factors that influence a person to become a smuggled migrant.