He's a naturalized US citizen. Moved to the US from Europe about 11 years ago. He married his current spouse before becoming a US citizen, the USCIS already knew about his current marriage based evidence submitted during N-400 process but he never filed I-130 petition for her to go over to the states.
I think we'd have a good chance with the Lagos consulate although we are unsure whether to get married here in Nigeria and file for CR1 or go for K1 fiance route since its faster when the divorce finalized