Bola

There is no ratified agreement between the U.S and any other country in the world that requires the U.S to recognize a divorce decree issued abroad   but there is one ratified agreement  used here that recognizes the foreign divorce if both parties had notice of the divorce proceeding and the chance to be part of the divorce proceedings  to be heard in the divorce proceedings, clearly you were not heard then his divorce decree from abroad is not valid.There is the possibility  that he faked your signature then I  advise you to write immediately to the US.CONSULATE in Nigeria, if she didn't leave Nigeria the U.S Consulate might cancel her spousal visa, and inform IN WRITTING TO THE CBP(CONTROL BOARD PATROL) as well, in case she didn't enter  yet she will see the CBP officer. You can go further informing USCIS that you never signed any divorce paper and the Department of State website specified a foreign divorce is not valid if both parties didn't have the chance to be heard and you were never informed of any divorce proceedings what led you to think your ex husband used fake documents showing he is divorced in order to get married to a Nigerian Citizen.You can inform all these 3 places and submit a copy of your marriage certificate as well.

Good luck

P.S I am an attorney.

Sandra SMS