I'm a U.S. citizen, engaged to be married to a man from another country. He has been to the U.S. many times, on the Visa Waiver Program. But now everyone is telling me that he has to go through the much longer process of getting a fiancé visa to come to the U.S. in order for us to get married and apply for his green card. Why can't he just come in on the Visa Waiver as usual and then we take care of the wedding and the green card paperwork after he gets here?
On the surface, your plan sounds sensible; but immigration law and common sense don't always match up. In fact, the plan you are suggesting would amount to a fraudulent use of the Visa Waiver Program (VWP), which could ultimately result in your new husband's application for lawful permanent residence (a green card) being denied.
Let's look at this step by step. Say your fiancé takes a long plane trip to the U.S., where an officer of Customs and Border Protection (CBP) greets him and asks about his purpose in entering the United States. Your fiancé says he's going to get married and apply for a green card. The CBP officer informs your fiancé that, because the Visa Waiver program is meant only for people coming to the United States for visits of no longer than three months (90 days) for either pleasure or business, and who have no intention of staying in the U.S. permanently, his entry is denied. Your fiancé would likely have to return to his country on the next plane.
Or let's say your husband successfully lies to the CBP officer and gains U.S. entry. The two of you get married and submit an application for adjustment of status (a green card) to U.S. Citizenship and Immigration Services (USCIS). At your green card interview, the USCIS officer notices that your wedding took place not long after the VWP entry, asks questions, and perhaps ultimately decides that your husband committed fraud upon entry and is therefore inadmissible. Your husband is denied the green card and placed into removal proceedings.
You and your husband would not be the first to make this or similar mistakes. In rare cases, and after paying a lot in legal fees, the applicant might qualify for a waiver of the fraud and receive the green card.
However, it's far easier to go the legal route and either apply for a K-1 fiancé visa now or get married overseas and then apply for an immigrant visa (the equivalent of a green card). See an experienced immigration attorney for a full analysis.