In the United States, federal law governs who may enter the United States, how long they may stay, and what they are permitted to do while in the United States (example: working).
Immigration benefits and enforcement are administered by the Department of Homeland Security (DHS). Prior to 2003 this organization was known as the Immigration and Naturalization Service (INS).
Under U.S. Immigration law, persons are either U.S. Citizens/Nationals or Aliens. Aliens can be lawful permanent residents (green card holders) or non-immigrant visa holders.
Typical immigration services that an attorney can help with include: