Can an American citizen legally marry an alien that is in the usa on a b1, b2 multiple entry visa ?

Sort of. It depends on what you intend to do once you are married.

Yes you can marry, unless your state requires you to establish residency and they may not accept such a visa, but probably yes. There is certainly nothing illegal about getting married.

The problem is that you cannot come to the US on such a visa INTENDING to get married or least not intending to get married and remain in the country; to do that is a violation of the B visa. You need a fiance visa for that.

Let's say you just plan to get married, have the non-citizen leave the country and then apply for permission to immigrate as a spouse, you can do that. But if you told the immigration officer at the port of entry, you would be denied entry because there would be a presumption of the intent to remain, and the visitor has to *prove* they will not remain, the government by law presumes that they will try to remain.

Now if you do get married and have a good story to tell, you can apply for an adjustment of status, remain in the US while you wait for your visa and green card. The story would explain how you came to be married without intending to get married when you entered the country.

But technically they can deport you and delay your reentry if they determine you did it knowing in advance.

I don't think they actually do that much though. I think in fact people do this pretty often. But technically you could be violating the terms of the visa and there can be consequences.

An American Citizen can marry his dog if he wants to. (well, that's an exaggeration). But listen up: An American Citizen can marry anyone he wants to. As long as both parties have some sort of ID and their birth certificates to bring to the Register of Deeds or Magistrate, (it varies from state to state), they can get married.

I think what you're wondering is if an American Citizen marries an alien on a b1/b2 visa entry, can the American Citizen legalize the alien?

The answer is yes.

Even if the b1/b2 overstayed his visa, but if he held on to his i-94, it shouldn't be a problem.

Yes you can legally marry ..and yes the visa holder should depart when their I-94 is up

Follow the flowcharts here

http://familybasedimmigration.com/forum/index.php

Yes. You need to get marriage license first though.

Marriage is not governed by immigration regulations.