US immigration law deals with legal issues and US policies relating to foreign nationals who come to the United States on a temporary or permanent basis, including the associated legal rights, duties, and obligations of aliens in the United States; the application processes and procedures involved with naturalization of foreign nationals who wish to become US citizens; as well as dealing with legal issues relating to people who are refugees, people who cross US borders by means of fraud or other illegal means, and those who traffic or otherwise illegally transport aliens into the United States. An immigration lawyer may assist clients with all aspects of immigration law, but many choose to specialize in subcategories of immigration law, due to the complexity of the law and the frequency of updates and changes. Specialization areas will include asylum/refugee law, business immigration law, and criminal and deportation defense. An attorney practicing in one of the above areas of immigration law may work for the government, a law firm, a community-based organization, or in-house for a company employing foreign nationals.