In an immigration context, marriage fraud is quite serious.
To convict a person under 8 U.S.C. 1325© the government must prove
1) the person knowingly entered into a marriage
2) the marriage was entered into for the purposes of evading a provision of the immigration laws; and
3) the person knew or had reason to know of the immigration laws. *
* the government does not need to prove that person knew of the specific immigration statute violated
Punishment: Imprisonment up to 5 years and up to $250,000 fine.