Since Sen. Obama has neither renounced his U.S. citizenship nor sworn an oath of allegiance to Kenya, his Kenyan citizenship automatically expired on Aug. 4, 1982.
Renouncement of citizenship is a request to terminate citizenship. Federal law gives any citizen who moves out of the country and establishes themselves as a citizen of another country or will obtain citizenship of another country the right to request a Certificate of Loss of Nationality.
Citizenship is not terminated until a CLN is issued. Only the President, through his Secretary of State, can issue a CLN. SCOTUS can offer an opinion on who should be issued a CLN and who should not be issued a CLN, but the final decision is up to the President alone. SCOTUS can only offer a nonbinding opinion. Congress passes bills establishing a uniform law of immigration and naturalization. Congress cannot issue CLNs or negate a CLN issued by the President.
Without a formal renouncement (request) by a citizen to forfeit their citizenship, the President can issue a CLN after the citizen has effectively renounced. An effective renouncement begins with a citizen notifying the State Department on their passport application they do not intend to return to the U.S. after a passport is issued.
A passport application ask the citizen where they are going, why are they going there and when are they returning to the U.S. These are not questions of idle curiosity. The State Department is establishing intent to maintain your U.S. citizenship. Telling the State Department you intend to live in Indonesia indefinitely, as Stanley Ann did, is the first step to informal renouncement of citizenship. Allowing your passport to exire, as Stanley Ann did, is the next step and all the SoS needs to issue a CLN.
So, when Obama says he didn't renounce his citizenship; he means his mother took the necessary steps to effectively renounce and SoS Dean Rusk issued him a CLN in 1967.