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 Wyoming, 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. While federal law oversees the status of these individuals, state laws may impact their daily lives, such as access to education, employment, and driver's licenses. However, the process for an unauthorized immigrant to adjust their status to a Lawful Permanent Resident (LPR) is exclusively a matter of federal jurisdiction. During the application process for LPR status, applicants remain unauthorized in terms of their immigration status until they receive their green card, even if they have been granted work authorization. Temporary Protected Status (TPS) holders 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.