Five years ago, after realizing that as an Indigenous man he was not recognized by Australia’s Constitution, Mr. Walubara quit his job as a political reporter and renounced his Australian citizenship and former name, Jeremy Geia. He returned his passport, public health care documents and driver’s license to their respective government departments, he says, and destroyed his Australian bank cards.

“I had assumed that I had true and correct membership inside the Commonwealth of Australia,” Mr. Walubara, who is now 45, recounted writing in the accompanying letters to each government department. “I have made a mistake: I’m no longer eligible for the benefits of your society,” he wrote. “Here are your instruments back.”

While experts say that Mr. Walubara has a long road ahead before Australia would recognize his claims to sovereignty, his argument has caught the attention of the public and the national news media.