He didn't "relinquish" it. It was ripped off of him kicking and screaming. He took it to the Supreme Court in an effort to retain it.
Look, this is simple. A "natural citizen" could have spent his entire life abroad, and never lost his citizenship for failing to live here for a designated period.
"Natural Citizens" are not subject to residency requirements. "Statutory citizens" are.
Any person will lose his citizenship if he knowingly takes expatriating actions. In Bellei's case he had been informed verbally and in writing that he was in danger of forfiting he natural-born citizenship unless he complied with the laws that identified him as a NBC to begin with. He did not do that, and was aware of the consequences of his actions. His citizenship wasn't stripped from him so much as relinquished through his own actions and with full knowledge of the consequences.
Look, this is simple. A "natural citizen" could have spent his entire life abroad, and never lost his citizenship for failing to live here for a designated period.
Depends on under what conditions a person's NBC status was recognized.