The purpose of this research is to find out the regulation on principle of nonrefoulement under international law, and how to implement the principle of nonrefoulement in Australia’s domestic policy in handling refugees and asylum seekers. Refugees are people that are forced flee their country of origin because they are threatened-suffered persecution and do not get protection from their country of origin. Before their status as refugees is declared legally by the law, they are called as asylum seekers. Refugees and asylum seekers have the rights to search and enjoy the rights to get asylum from other countries based on Article 14 of the Universal Declaration of Human Rights. In order to find protection from international community, refugees and asylum seekers are protected by the principle of non-refoulement, which is the basic rights of protection for refugees and asylum seekers regulated in 1951 Convention Relating to the Status of Refugees (1951 Refugee Convention) as the main instrument in international law relating to the status of refugees. The principle of non-refoulement is also enshrined in other international law instruments related with human rights. In particular, the principle of non-refoulement has been considered as Customary International Law, particularly as jus cogens (non-derogable norm) so that it cannot be ruled out by every member countries of 1951 Refugee Convention, to which reservation is not allowed. As a member state that has ratified the principle of non-refoulement as a domestic law, Australia is supposed to dutifully implement the principle of nonrefoulement in handling refugees and asylum seekers. However, in reality, Australia has indicated violations of the 1951 Refugee Convention. Through this research, the Writer tries to elaborate the interpretation of the principle of non-refoulement in Australia’s domestic policy in handling refugees and asylum seekers especially those entering Australia by sea.