What does an illegal alien have to do to become leagal?

Illegal immigrants cannot become permanent residents or obtain citizenship by marrying a US citizen or any other means, such as having a child born of such a marriage or relationship. A person who is illegally within the US will be required to voluntarily leave the country or when apprehended will be detained and in the vast majority of cases deported. The exception might be if the foreigner qualifies as an asylee or a refugee under the current Immigration laws.