If he claimed status as a "foreign student", then he made - without question - a fraudulent claim and may have committed perjury if his application was a sworn statement. Every piece of case law - and one in particular Kawakita v. U.S - says that he would have been a US citizen, regardless of what other nationality he may have actively sought and was granted. You can't be a "foreign" citizen if you hold US citizenship. Unfortunately, the statute of limitations in California (Occidental is located in CA) for fraud was three years in the 1980's. California authorities wouldn't investigate a case that's gone as stale as this on.
If there was Federal money involved, Title 18, § 3282 of the US Code sets 5 years for the limit of prosecution, trial, conviction or punished for non-capital offenses. The FBI wouldn't investigate something that could no longer be prosecuted. It is, as they say, water under the bridge.
Even if he was in no legal jeopardy however, he would certainly do anything he could to avoid the tidal-wave of bad publicity from such an egregious offense.
Barry was an Indonesian citizen in 1980 when his mother made pleading in her divorce to the court that TWO legal children were in the marriage to Lolo Soetoro, with one being a minor (Maya) and one over eighteen (Barry) in need of financial assistance for education. Barry, by entering Occidental as an Indonesian citizen abrogated his American citizenship and could only then regain it via statute appeal.