Despite recognizing Indigenous title to land in the early 1990s, Australia's domestic law has consistently refused to accommodate Indigenous claims of sovereignty or self-government. Unlike other common law countries, Australia's High Court continues to propagate the legacy of terra nullius by maintaining that sovereignty claims are non-justiciable by the courts of that state. It claims that the original assertion of sovereignty over Australia by the British is an "act of state" that cannot be challenged. By comparing the reasoning of the Australian High Court with that of the US Supreme Court and Canadian courts, I argue that the High Court's unwillingness to draw these claims into domestic jurisdiction reflects a construction of sovereignty that is unsustainable and unconvincing. Like its common law neighbours, Australia's highest court should acknowledge that the structure of authority in a state is a legitimate issue for its courts, and should deal substantively with the claims of Indigenous Australians.