When he was born? Maybe you should.
Barack most likely acquired Indonesian citizenship as a boy when he was adopted by Lolo Soetoro. He had no control over that and it does not affect his citizenship or his eligibility to run for President.
You can be a citizen and still NOT be eligible to run for President. If Barack voluntarily help dual citizenship as an adult, he would still be a citizen of the US but ineligible to run for President.
Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)