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 Connecticut, as in other states, the unauthorized or undocumented resident immigrant population includes individuals who entered the United States without proper inspection or overstayed their visas. These individuals are not considered legal residents under federal law. Unauthorized immigrants in Connecticut may apply for an adjustment of status to become Lawful Permanent Residents (LPRs) under the Immigration and Nationality Act (INA). However, until they are granted a green card, they remain unauthorized, despite possibly having work authorization. Temporary Protected Status (TPS) beneficiaries are a distinct category; while they do not have a permanent immigration status, they are not considered unauthorized because TPS provides a temporary lawful presence and work authorization in the United States. It's important to note that immigration law and enforcement are primarily federal matters, and state laws may provide certain protections or policies affecting undocumented residents, but they do not change an individual's immigration status under federal law.