Stanley Ann Dunham returned to the US in October, 1971 and on arrival in Honolulu was told that her US passport had expired in August, 1971. She was allowed into the US and in January, 1972 was issued a new US passport.
If she was an Indonesian citizen, it was for two months.
Barak Obama returned to the US in June/July of 1971, if he had a US Passport it would have expired in August, 1971.
In September, 1967, the State Department investigated the citizenship status of Barack Obama as part of an investigation of Lolo Soetoro’s status.
W. L. Mix wrote that “The person in question is a United States citizen by virtue of his birth in Honolulu, Hawaii, Aug. 4, 1961. He is living with the applicants spouse in Honolulu, Hawaii. He is considered the applicants step-child, within the meaning of Sec. 101(b)(1)(B), of the act, by virtue of the marriage of the applicant to the childs mother on March 5, 1965.
The section of the 1952 McCarron - Walters Act stated by Mix reads:
Section 101 (b) As used in titles I and II -
(1) The term child means an unmarried person under twenty-one years of age who is -
(A) a legitimate child; or
(B) a stepchild, provided the child had not reached the age of eighteen years at the time the marriage creating the status of stepchild occurred; or
(C) a child legitimated under the law of the childs residence or domicile, or under the law of the fathers residence or domicile, whether in or outside the United States, if such legitimation takes place before the child reaches the age eighteen years and the child is in the legal custody of the legitimating parent or parents at the time of such legitimation.
So in 1967 Obama had not been adopted by Soetoro and was referred to as a “stepchild”.
If he was adopted after 1967, he would have been to old to acquire Indonesian citizenship automatically by adoption and would have had to go through the Indonesian naturalization laws when he turned 21.
Law No. 62 of 1958, Law on the Citizenship of the Republic of Indonesia:
Article 2.
(1)A foreign child of less than 5 years age who is adopted by a citizen of the Republic of Indonesia acquires the citizenship of the Republic of Indonesia, if such an adoption is declared legal by the Pengadilan Negeri at the residence of the person adopting the child.
Article 5.
(1)The citizenship of the Republic of Indonesia because of naturalization is acquired with the validity of the decree of the Minister of Justice who grants this naturalization.
(2)In order to present a petition for naturalization, the petitioner shall:
a. have reached the age of 21;
b.be born within the territory of the Republic of Indonesia or at the time of presenting the petition be domiciled in said region for at least the last 5 consecutive years or in total 10 inconsecutive years;
http://www.refworld.org/cgi-bin/texis/vtx/rwmain?docid=3ae6b4ec8