Who owns the Benin Bronzes? The answer just got more complicated

After years of ignored pleas and stonewalled requests, deals were finally coming together to return some of Africa's most prized treasures to the continent.

The Smithsonian Institution, the Metropolitan Museum of Art and the German government announced they were returning scores of sculptures, plaques and ornaments, known as the Benin Bronzes, that British soldiers had plundered in 1897 from Benin City, in what is now Nigeria but was once the center of a kingdom. Plans were underway for a glittering new museum designed by British Ghanaian architect David Adjaye to showcase and protect the returned treasures.

But that plan has run aground since Nigeria's outgoing president announced he had transferred ownership of the looted items to a direct descendant of the ruler they had been stolen from. At a moment when museums worldwide are trying to come to grips with contested...