His father wasn't a US citizen, he was an alien.
He
had to be naturalized...cut and dry.
The Immigration and Nationality Act of 1952 (Pub.L. 82–414, 66 Stat. 163, enacted June 27, 1952), also known as the McCarran–Walter Act,
codified under Title 8 of the United States Code (8 U.S.C. ch. 12), governs immigration to and citizenship in the United States. It has been in effect since June 27, 1952. Before this Act, a variety of statutes governed immigration law but were not organized within one body of text.
Title 8 of the United States Code outlines the role of aliens and nationality in the United States Code
Don't forget he was adopted by Sotero in Malaysia and they don't allow for dual citizenship and he traveled to Pakistan with his college boyfriend in 1981 and they did not allow Americans in at that time, so he had a Malaysian passport.