The unauthorized or undocumented resident immigrant population is defined as all foreign-born non-citizens who are not legal residents. Most unauthorized residents either entered the United States without inspection or were admitted temporarily and stayed past the date they were required to leave.

Unauthorized residents applying for adjustment to lawful permanent resident (LPR) status under the Immigration and Nationality Act (INA) are unauthorized until they have been granted lawful permanent residence (a green card)—even though they may have been authorized to work. Persons who are beneficiaries of Temporary Protected Status (TPS) are not technically unauthorized.

In Wisconsin, as in all states, the definition and treatment of unauthorized or undocumented resident immigrants are primarily governed by federal law, specifically the Immigration and Nationality Act (INA). Unauthorized immigrants are those who have entered the United States without proper inspection or have overstayed their visas. While Wisconsin state law does not define unauthorized immigrants, it is subject to federal regulations and statutes that address immigration status and enforcement. Unauthorized immigrants in Wisconsin may apply for an adjustment of status to become Lawful Permanent Residents (LPRs), but they remain unauthorized until they receive their green card. Additionally, those with Temporary Protected Status (TPS) are considered to be lawfully present in the U.S. and are not classified as unauthorized, although TPS is a temporary benefit that does not directly lead to LPR status. It's important to note that while state and local authorities may have policies regarding the treatment of undocumented immigrants, immigration enforcement and the adjustment of immigration status are federal matters.