Immigration Law refers to national government policies which control the phenomenon of immigration to their country. Immigration law is related to nationality law, which governs the legal status of people, in matters such as citizenship. Immigration laws vary from country to country, as well as according to the political climate of the times, as sentiments may sway from the widely inclusive to the deeply exclusive. Immigration law regarding the citizens of a country is regulated by international law.

Federal immigration law determines whether a person is an alien, the rights, duties, and obligations associated with being an alien in the United States, and how aliens gain residence or citizenship within the United States. It also provides the means by which certain aliens can become legally naturalized citizens with full rights of citizenship. Immigration law serves as a gatekeeper for the nation's border, determining who may enter, how long they may stay, and when they must leave.

By controlling the visa process, the federal government can achieve the goals of its immigration policies.  There are two types of visas: immigrant visas and nonimmigrant visas. The government primarily issues nonimmigrant visas to tourists and temporary business visitors. The government divides nonimmigrant visas into eighteen different types, but for most types, does not impose a cap on the number that may be granted in a year. Only a few categories of non-immigrant visas allow their holders to work in the United States. Immigrant visas, on the other hand, permit their holders to stay in the United States permanently and eventually to apply for citizenship. Aliens with immigrant visas can also work in the United States. Many immigrant visas remain subject to per-country caps.

Deportation refers to the official removal of an alien from the United States.  The U.S. government can initiate deportation proceedings against aliens admitted under the INA that commit an aggravated felony within the United States after being admitted.  An alien's failure to register a change of address renders the alien deportable, unless the failure resulted from an excusable circumstance or mistake.  If the government determines that a particular alien gained entry into the country through the use of a falsified document or otherwise fraudulent means, the government has the grounds to deport.