About Immigration Laws for Marriage
Virtually all countries allow for the alien spouses of their citizens to legally immigrate and reside in the country of their spouse based on the couple's marriage. United States immigration laws allow for such legal residence in the United States, so long as the couple can prove the marriage was entered into in good faith.
The United States immigration laws regarding marriage based immigration are considered particularly stringent. They are designed to deter marriages that are a sham designed to obtain legal residency. These laws include:
K-1 visas
As the foreign fiancé(e)s of U.S. citizens to whom one is not yet married, a person is entitled to apply for this visa. It allows that fiancé(e) to enter the U.S. for the purpose of marrying their U.S. citizen fiancé(e).
The visa must be obtained outside of the United States at the consulate. It requires an interview during which the applicant must "prove" the relationship.
K-3 visas
As a foreigner who has already married a U.S. citizen, you are entitled to apply for this visa. In order to obtain the visa must, the foreign spouse needs to apply in the country where the marriage took place. Once in the United States, the foreign spouse must file for permanent residency through the U.S. Citizenship and Immigration Services.
Legal Permanent Residents (LPR)
Legal permanent residents (green card holders) cannot bring their fiancé(e) into the United States on a K-1 visa. The couple either needs to wait until the LPR becomes a U.S. citizen or, they need to marry outside of the United States and file for a family-based visa.
K-3 visas are available for spouses of LPR
They are not immediate however. The United States caps the number of immigrant visas issued annually and once the number is reached, visa distribution ends for the period. Spouses of LPRs have waited up to five years for a visa to become available.
Marriage-based legal residents
They can apply for citizenship after three years of residency in the United States. The conditions are that they are still married to the same U.S. citizen and have not committed any felonies during their residency.
If a green card is issued
If it is based on a marriage that is less than two years old when the person becomes a permanent resident, the resident status will be conditional for two years. At the end of the two years, the resident status expires unless a petition to remove the condition is approved by the immigration authorities.