United States immigration laws are federal legislation and apply to all states equally. To marry a United States citizen and live lawfully in the United States, foreign nationals must comply with the relevant immigration, citizenship and naturalization laws. The government agency that administers immigration laws is the United States Citizenship and Immigration Services (USCIS).
To enter into the U.S. to marry a U.S. citizen a foreign national must first secure a K-1 fiance visa. The U.S. citizen fiance must file form I-129F, Petition for Alien Fiance, with the USCIS. If the petition is approved it will be forwarded to the U.S. consulate or embassy in the foreign national's home country. The national will then attend the consulate or embassy to be interviewed, and have the visa issued. The visa does not give a 100% guarantee of entry at a U.S. port of entry; the foreign national may be further interviewed and refused entry.
Upon marriage, the foreign national needs to file an Adjustment of Status, form I-485, to become a legal permanent resident and get authorization to work. The applicant may remain in the U.S. to await the change of status, providing their K-1 visa is still valid. Processing times can be 12 to 18 months.
To ensure the validity of the marriage and that it was not entered into for solely immigration purposes, marriage-based permanent residency is granted conditional residency for a temporary period of two years. After two years, the foreign national must file for Removal of Conditions to get a permanent resident card. At this time the foreign national and U.S. citizen should still be living together as a married couple. After five years of permanent residency, the foreign national may file for naturalization to become a U.S. Citizen.