Congress’ Homeland Security Act of 2002 created the Department of Homeland Security a year after the September 11, 2001 attacks. According to its founding documents, the agency’s stated purpose is to prevent terrorist attacks, reduce the vulnerability of the United States to terrorism and act as a focal point for natural and manmade disaster response. The charter also makes note of agency’s responsibility to investigate the connection between drug trafficking and terrorism.
The creation of DHS was the largest federal government reorganization since the creation of the Department of Defense in 1947; it consolidated 22 agencies and bureaus into DHS. Immigration responsibilities were transferred from the Immigration and Naturalization Services and two smaller agencies to the newly founded department. The job of enforcing immigration law was given to a newly formed agency called Immigration and Customs Enforcement (ICE). Immigration policy became centralized under one agency and wider immigration powers were given to the Attorney General and Secretary of Homeland Security.
Prior to the creation of the DHS, the State Department Bureau of Consular Affairs and the Justice Department Immigration and Naturalization Service administered law and policy on issues of immigrants. The 2002 act centralized these services and gave the executive branch more oversight capacity over who enters and leaves the country.