It is known that when a man is legally married to a wife and he wants to take another according to his faith within a Muslim community, it is done by contract. Either a written and legally binding contract or by a document prepared formally to recognize the union and signed by at least 15 or more members of the community. I have witnessed same and know they exist in the USA. The contracts with innumerable witnesses have a festive art within framing the written contract.
In the USA such a document could be litigated as palimony.
In the USA such a document could be litigated as palimony.