US Immigration and Naturalization laws created by Congress are administered by several different federal agencies. The Department of State handles visas, the Department of Justice prosecutes those who violate immigration laws and the Department of Homeland Security administers ports of entry into the US. For more information on US immigration laws speak to a qualified immigration and naturalization attorney or if outside of the US, US embassies or consulates can help you with understanding US policies and procedures on immigration and naturalization.