Indonesian law has no effect on US Citizenship. Only US law applies. To prove that Obama is no longer a citizen, you would need not only to show that he aquired Indonesian citizenship, but that his mother intended for him to renounce his American citizenship. You can’t lose US citizenship by accident or oversight. It must be an explicit and intentional act under US law.
http://travel.state.gov/travel/cis_pa_tw/cis/cis_1753.html
“In order to lose U.S. citizenship, the law requires that the person must apply for the foreign citizenship voluntarily, by free choice, and with the intention to give up U.S. citizenship.”
BHO, while a minor was not in a position to renounce his citizenship. His mother’s actions, in returning him to the US, show intent not to renounce citizenship. She also never filled out any document with the US Embassy renouncing her or her son’s US citizenship, therefore, he is a citizen.
US State Department policy on renouncing US Citizenship.
http://travel.state.gov/law/citizenship/citizenship_778.html
Below is an FAQ on dual citizenship from a dual citizen.
Tell me something then....why does our nation have laws that say that a eighteen year old must reaffirm his citizenship or lose it after six months of becoming eighteen.
If Indonesian laws means nothing to our laws why have such a law on our books at all?
Clearly our laws recognize that a minor could or would want to reaffirm their American Citizenship when they became an adult and our laws also say that if they didn’t do so they could lose their American citizenship as well.
Obama’s mother knew what having her son adopted in Indonesia meant, it meant he would lose his American citizenship, and she was prepared to do that and more. Under Indonesian law Lolo Soetoro became Barack Obama’s only legal guardian, since his mother had no legal rights under Indonesian law. In order to attend any Public schools in Indonesia, Barry Soetoro had to become an Indonesian citizen.
And unless the State department has records of him following the proscribed procedure for reaffirming his American citizenship at 18 he lost it according to US law.