국제법의 가장 중요한 주체인 국가는 항상 동일한 형식으로 존재하는 것은 아니며, 국가의 생성, 영토의 취득, 합병, 분열 및 분리, 소멸 및 부활이 계속적으로 발생해왔다. 이 경우에 신국가가 구국가와 동일한 국가인지 여부가 문제되는데 이는 관련당사국의 이해관계뿐 아니라 기존 조약의 계속성 및 국제책임의 근거 등을 위해 중요한 문제이다. 이와 관련 국제법 이론과 독일, 오스트리아, 러시아, 발트3국 등 주요국의 국가실행을 검토한다. 우리나라는 1986년에, 대한제국이 1910년 이전에 체결한 다자조약 중 당시까지 유효한 3개의 조약이 대한민국에 계속 적용된다는 선언을 하였다. 이는 대한민국이 대한제국의 동일성과 계속성을 가지고 있는 국가임을 대내외에 법적으로 확인한 사례이다. 발트3국은 1940년 소련에 의해 강제병합되어 소련 내의 소비에트공화국으로 편입되었다. 동 국가들은 51년간 소멸하였다가 1991년 소련으로부터 주권과 독립을 회복했으며, 독립 후 소련에 강제병합되기 이전의 구국가의 동일성과 계속성을 승인받았다. 발트3국의 동일성과 계속성 승인은 이 나라들이 국제법 측면에서뿐 아니라 국제정치 측면에서도 소련에서 분리된 국가가 아닌 동유럽국가로 인정되게 하였고, 이에 따라 유럽연합(EU)과 북대서양조약기구(NATO)에 가입할 수 있었는데 이는 국가의 계속성이 국제정치적으로 어떻게 작용할 수 있었는지를 보여주는 중요한 사례이기도 하다. 한국의 1986년 대한제국 다자조약의 효력 확인 사례와 발트3국의 사례는 불법행위로 이뤄진 국가의 병합은 아무리 오랜 세월이 흘러도 정당화될 수 없다는 관습법을 확립한 것으로 사료된다. 마지막으로 최근 학계 등 일부에서 제기된 건국절 제정 논란과 관련하여 중국, 프랑스 등의 사례 및 대한제국의 다자조약 효력 확인조치와 북한과의 관계 등을 검토하고, 건국절 제정이 국제법과 국제관행 및 우리 정부가 취한 조치와 양립할 수 없음을 주장한다.

States do not remain constant in form because of an acquisition or loss of land, a revolutionary change of government or a belligerent occupation. Despite these changes, a state remains as the same state or maintains its identity and continuity. The issue of state identity and continuity had not been raised frequently in international law until the break-ups of the Soviet Union and Yugoslavia in the 1990s. This issue has rather been regarded as one of international politics than international law. However, there were complex legal questions about ‘resurrected states’ which had ceased to exist for some time but reestablished thereafter as an identical state such as Austria after the Second World War. The Baltic states (Estonia, Latvia and Lithuania) restored their sovereignties and independences in 1991 from the Soviet occupation, which had lasted for more than 50 years. By restoring their independences, they have been recognized as continuing states before the occupation in 1940. The continuity of the legal identity of the Baltic states enabled them to reestablish themselves as the erstwhile Eastern European states, hence they could join the European Union (EU) and the North Atlantic Treaty Organization (NATO). Besides that, there are several other states which have been regarded as the identical and continuous states after the cataclysmic changes such as Germany (then West Germany after the Second World War). In case of the Russian Federation, it is the continuing state of Imperial Russia before the Russian Revolution in 1917, and the Soviet Union before the its break-up in 1991. The Republic of Korea(ROK, South Korea) has long claimed the continuity of the legal identity of the Empire of Korea, which was forcefully annexed by Japan in 1910. It has the view that all the treaties concluded with Japan before August 1910 was null and void from the beginning(ab initio), since it was concluded against the will of the Korean Emperor who were coerced to ratify them. When Korea and Japan normalized their relations in 1965, the two countries agreed that all the bilateral treaties concluded before the forced annexation in 1910 was already ‘null and voi’’. The ROK has recognized the legitimacy of the Provisional Korean Government (Government-in-exile) established in China in 1919 at its preamble of the Constitution. Also, the Government of the ROK, following the general election in Korea in 1948 under the auspices of the United Nations (UN), was recognized as the ‘only legitimate Government of Korea’ by the Resolution 195(III) of the UN General Assembly in 1948. This resolution clearly demonstrated the fact that ‘A State of Korea existed’, since this was regarded as the recognition of government, not the recognition of state. The ROK declared in 1986 that the three multilateral treaties ratified or acceded by the Empire of Korea before 1910 would continue to be applied on the basis of the continuity of the legal identity of the state. It also notified that effect to the depositary state (The Netherlands) of those treaties and other states concerned. The cases of the Baltic states and Korea are supported by the principle of international law of “ex injuria non oritur jus”, which means that no legal benefit can be derived from an illegal act. In view of the South Korean government declaration in 1986 on its identity and continuity of the Empire of Korea before 1910 and other international practices of the continuity of state, it is not necessary to deliberate further on the recent controversy over designating new national creation (or foundation) day on 15th August 1948 when the government of ROK was officially established.