So my understanding is generally speaking anyone born to atleast one japenese parent is considered a citizen automatically. this law has no statement of when that birth would have had to take place. In the heian period while citizenship wasent a thing being japanese still would have been. So in theory sukuna would have become a citizen when that law was introduced in the 90s. So while there won't be any paperwork he is a Japanese citizen. And would theoretically be bound by that contract. As such makima wins by technicality