The United States immigration law regulates the entry into the United States, the length of stay, what is allowed to be done during the stay in the country, and when they must leave. Immigration law also controls who can be admitted as permanent residents and naturalized US citizens. The United States Congress legislates the laws and periodically updates the laws that regulate immigration.
Immigration in general is a matter of federal law, and not state law. Immigration benefits and compliance with the laws are administered by the Department of Homeland Security (DHS); which is composed of the three agencies:
United States Citizenship and Immigration Services. (USCIS): USCIS manages immigration benefits, processes naturalization applications, legal permanent residence (“green card” status), nonimmigrant visas, work permits, political asylum, and other immigration benefits.
Immigration and Customs Control Service of the United States. (ICE): ICE applies federal laws governing border control, customs, commerce and immigration to promote internal security and civil protection.
United States Office of Customs and Border Protection (CBP): CBP controls the entry of people and goods to the United States., And is responsible for keeping weapons and terrorist groups out of the country.
Under United States immigration laws, people are US citizens or foreigners. Foreigners are classified according to their immigrant status. Foreigners can be legal permanent residents (green card holders), non-immigrant visa holders, foreign citizens with other types of legal stays, or undocumented individuals. The status class determines your rights and responsibilities.