Supposedly only Nigerian nationals can adoption from Nigeria. I cannot find any adoption agencies nor any confirmation on ANY legal method for Americans to adopt from Nigeria--only repeated information that its not possible. However, the State Dept reports that 70+ children entered the US on orphan visas from Nigeria last year. Seems to me, that is too high to just be familial adoptions by Nigerian nationals.

OTOH, I've heard a few people speculate that perhaps the Nigerian system is super curropt and its easy to override the laws with bribes.

Wish I could tell you more. I've searched for answers to this question for about 18 months at this point without any clear answers.