The number of aliens unlawfully residing in the United States
has grown to an estimated eleven million in 2009. Dissatisfaction with federal efforts to control unauthorized immigration has led some states and localities to consider, and in some cases implement, measures intended to deter the presence of unauthorized aliens within their jurisdictions. Although some states and localities, which are concerned with the presence of unauthorized aliens, have been content to communicate with federal immigration enforcement officers under limited circumstances, other jurisdictions have taken a more active role, including through direct enforcement of federal immigration laws. Some states and localities have gone further, but refrain from taking a more active role in deterring illegal immigration. Others have worked cooperatively with the federal government to actively enforce federal immigration law. Some jurisdictions have taken a more robust approach to deterring illegal immigration by imposing their own regulatory restrictions upon unauthorized aliens’ access to employment and housing.