According to the U.S. State Department, U.S. citizenship must be surrendered voluntarily by an adult, or by an older minor who convinces a consular officer that he is acting voluntarily and understands the gravity of his actions. A parent cannot renounce your citizenship on your behalf.
If he used an Indonesian passport to travel to Pakistan in 1981, he’s toast.
Also false. Holding a passport from another country has no effect on U.S. citizenship. A U.S. citizen must use a U.S. passport to enter or exit the United States; aside from that, the U.S. government takes no interest.
Revision to citizenship law imposes more restrictions - Saturday, June 26, 2004
The citizenship law is designed to prevent apatride (stateless) or bipatride (dual citizenship). Indonesian regulations recognize neither apatride nor bipatride citizenship.
In an attempt to prevent dual citizenship, the draft revision includes new regulations.
A foreign child aged below 21 and unmarried, who is adopted by an Indonesian, will be eligible for Indonesian citizenship if the process does not cause dual citizenship.
Draft revision of citizenship law No. 62/1958
These laws were passed in 2004. The original one it amended was from 1958. Indonesia has never allowed dual citizenship.
There was also an "exit control" law in Pakistan in 1981. You may get in but leaving was not a sure thing.
Exit from Pakistan (Control) Ordinance, 1981
This is also interesting.
1981 - Obama Visits Pakistan When All Non-Muslim Vistors Unwelcome - Bin Laden There, Too
Pakistan was in turmoil in 1981 and ruled of martial law. Millions of Afghan refugees were living in Pakistan, while the Afghan Mujahedeen operated from bases inside Pakistan in their war with the Soviets. One of the leaders that based his operation in Quetta, Pakistan was Usama Bin Laden (The Sheik).
Pakistan was on the banned travel list for US Citizens at the time and all non-Muslim visitors were not welcome unless sponsored by their embassy for official business.