West Papua was incorporated into Indonesia under the 1962 New York Agreement, which was signed between the Netherlands and Indonesia without involving indigenous West Papuans. The Agreement attempted to legitimise Indonesia’s claim of sovereignty over West Papua. It is the narrative around this Agreement that effectively dictates indigenous West Papuans' lives, including their subjugation to historical and ongoing human rights violations. This thesis closely examines the legal grounds of Indonesia’s claim, with a particular focus on whether the New York Agreement was legitimately and authentically implemented through the processes of the 1969 Act of Free Choice. Using primary and secondary sources, this thesis examines the legality of Indonesia’s occupation in West Papua. It begins with the circumvention of international laws that prevented indigenous West Papuans from gaining the benefit of international decolonisation regimes during international decolonisation periods, which ultimately led to the re-colonisation of West Papua. A careful historical examination confirms that the indigenous people of West Papua have lost their legitimate standing in international law. The thesis contends the intentions behind the creation of the New York Agreement were not genuine, but that the Agreement was a purposely imposed colonising law to recolonise the territory. By employing key legal arguments, this thesis contends that Indonesia's sovereignty claim over West Papua is legally invalid, historically unjustified and morally unacceptable. On reviewing both historical and ongoing violations of the human rights in the region, this thesis further argues that an internationally mandated process of self-determination should be considered as a legal remedy. The claims of indigenous West Papuans are historically supported, legally grounded and empirically demonstrated. This thesis establishes legal frameworks within the international law and institutions that can be utilised as practical pathways to West Papuan self-determination, with a particular focus on options within the United Nations systems.