If a F1 student did an arrange marriage in Nepal with a US citizen of Nepali origin and then they both came back to the US without letting the US authorities know about their wedding, how would the US authorities ever find out that the F1 student has been married and therefore "broken the law"? Unless you do a court marriage or register your marriage somewhere in Nepal or unless you tell the US authorities that you have been married in Nepal, there is really no proof of that arranged marriage.