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 Michigan, as in all states, the definition and regulation 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. These individuals are not considered legal residents until they adjust their status to Lawful Permanent Resident (LPR), commonly known as obtaining a green card. During the application process for LPR status, they may be authorized to work in the U.S., but they remain unauthorized residents until their application is approved. Temporary Protected Status (TPS) beneficiaries are granted temporary relief from deportation and work authorization, but they are not considered unauthorized immigrants while under TPS protection. It's important to note that while states like Michigan may have policies that impact immigrants, such as access to state services or law enforcement practices, the overarching immigration status and pathways to legalization are dictated by federal law.