Waiver Requests for Conditional Residents Filing I-751
Not every immigrant who obtains conditional residency through marriage to a U.S. citizen is able to complete the process of obtaining a permanent green card in the expected way -- by having the U.S. spouse sign onto a petition to remove the conditions on residency, on Form I-751.
Various life circumstances can get in the way; a spouse's death, marital separation, divorce, or simply bad relations. Fortunately, given that the immigrant may by now have become quite settled in the United States, and perhaps even be raising U.S. citizen children here, the law allows exceptions to the joint filing requirement in certain situations. The immigrant still needs to file Form I-751 by the deadline, but can do so without the spouse's help, by asking for a waiver, as described here.