Entering the United States without approval from U.S. immigration authorities is illegal. So is staying in the U.S. without permission after a visitor visa, work or other visa, or other authorized stay has expired. Even violating the terms of a legal entry to the United States can make a non-citizen's stay illegal.
U.S. immigration law offers few options to go from being an illegal or undocumented immigrant to a U.S. permanent resident (with a green card). We briefly describe the most likely possibilities below, but you should see an attorney for further help.
Entering into a valid, bona fide (real, not sham) marriage with a U.S. citizen (of the same or opposite sex) makes you an "immediate relative" under the U.S. immigration laws. An immediate relative is theoretically eligible for a U.S. green card just as soon as the person can get through the immigration application process. However, your current illegal status in the U.S. could create problems.
If you are in the United States illegally because you stayed past the expiration date on a valid visa, rather than having entered illegally (without inspection), consider yourself lucky: Your legal entry qualifies you for an exception, under which you should be able to apply for your marriage-based green card without leaving the United States, using a procedure called "adjustment of status."
If, however, your most recent entry into the United States was illegal; for example, you crossed the U.S. border in secret, without stopping at an inspection point; you have little chance of adjusting your status to permanent resident based on your marriage. That's the law's way of punishing people for unlawful entry. The exception is if you are covered by some very old laws, such as what's called "Section 245(i)" (get a lawyer to analyze this).
If you aren't eligible to use the adjustment of status procedure, you will have to attend the interview for your green card (which is the last step in the application process) at an overseas U.S. consulate in your home country (called "consular processing"). However, at that point the consulate could penalize you for your illegal U.S. stay, with a time bar on returning to the United States. The penalty is either to spend three years outside the United States if you stayed in the U.S. illegally for six months (180 days) or more; or to spend ten years outside the United States if you stayed in the U.S. illegally for one year or more.
If you haven't yet been in the United States illegally for six months or more, you might want to leave right away in order to make use of the consular processing possibility.
If you have already spent more than six months in the United States illegally, talk to an immigration lawyer. You might qualify for a "waiver," (legal forgiveness, ideally on Form I-601A if no other grounds of inadmissibility are a hurdle in your case). A waiver would allow you to reenter the United States right away after your consular processing interview, but this waiver is hard to get. You would need to prove that your being denied the immigrant visa (green card) would cause extreme hardship to one or more of your U.S. citizen family members.
Getting married to a lawful permanent U.S. resident (a green card holder rather than a citizen) will also technically make you eligible for a U.S. green card, but because you could are not an "immediate relative," you cannot use the adjustment of status procedure. That means you'd have to go through "consular processing" as described above, with all the risks that entails.
If you serve honorably and on active duty with the U.S. Armed Forces during one of the wars or conflicts named below, the law allows you to apply for U.S. citizenship. You don't have to go through the usual step of applying for a green card first. You must, however, enlist (sign up) while on U.S. territory, such as the Canal Zone, American Samoa, Swains Island, or a noncommercial U.S. ship.
The conflicts that qualify you for immediate U.S. citizenship include:
If you are arrested by U.S. immigration authorities, you might be able to avoid removal, and receive a U.S. green card, if you can prove all of the below:
Don't attempt to apply for cancellation of removal on your own. It is available only if you are already in immigration court (removal) proceedings and facing deportation. You'll definitely need a lawyer's help in this situation.
You can apply for the right to stay in the U.S. if you qualify for asylum and apply within one year of your entry or the expiration of your authorized stay. You'll need to show that you have been persecuted, or fear future persecution, in your home country, based on your race, religion, nationality, political opinion, or membership in a particular social group.
The process involves submitting USCIS Form I-589, together with detailed documentation of your membership in the group that you claim and the persecution that you faced or fear.
If you are granted asylum, you can apply for a green card one year after your approval, and for U.S. citizenship four years after that. (If denied, you could be deported, unless you can show that you would likely face torture upon return.)
If you come from a country that has recently had a civil war, environmental or natural disaster, or other trouble that makes it unsafe for its citizens to return there, the United States might offer what's known as Temporary Protected Status or "TPS."
This is not a green card, nor does it lead to a green card. However, TPS would allow you to stay in the United States legally for a set amount of time (maximum 18 months), and to receive a work permit while you're here. See the TPS page of the USCIS website for details and the list of currently eligible countries.