According to Amemrican citizenship law, a minor cannot yield his American citizenship. Nor can a parent yield it for him.
If Obama actually held dual citizenship, it was up to him to declare one way or the other upon his 18th (or 21st...it's been a long time since I studied International Law).
If, as an American citizen, he misrepresented himself as an Indonesian citizen for the purpose of gaining an advantage at Occidental, it would be a clear-cut case of fraud.
I can't imagine that Occidental would prosecute the case, though.
Thank you