Im a Columbia alum as well and I know that Columbia doesnt accept transfers from colleges like Occidental without special reasons/circumstances.
Im betting that his transfer application was made and granted on the basis of his claim to be a foreign born student. Columbia loves diversity in the student body and this would account for the approval of his application.
Further, there is an indication in his life story that Percy Sutton, a well-knowN black politician in NYC who was also Malcolm Xs attorney was his sponsor. How does a guy from Hawaii get support from a radical pol from NYC unless it was through radical connections such as FRank Marshal Davis, the Communist or Bill Ayers the radical Weatherman?