第二次世界大战后，反殖民主义运动的兴起和冷战的爆发使得旧有国际法秩序受到挑战，国际政治形势呈现新特点。在此时代背景下，越南领土上同时存在北越、南越两个政权，均宣称代表全体越南人民行使主权。二者彼此敌视，采取截然相对的外交政策，分别得到东方国家阵营和西方国家阵营的承认和援助。直至1975年，北越才通过军事力量推翻南越，并于次年建立统一的越南社会主义共和国。 越南争取民族独立和统一的斗争持续上百年。法国的殖民统治和此后两政权的并立，都使得越南的国际法主体资格出现争议，如越南在法律上是否始终是一个国家，哪一政权可以合法代表越南实施国家行为。由于国际法主体资格是决定相关实体国际法权利和义务的起点，厘清该问题具有重要现实意义。文章的时间跨度限定在19世纪60年代至20世纪70年代，即自法国开始确立殖民统治至越南实现最终统一。文章采用实证研究的方法，通过档案文献还原越南历史原貌，同时以一般国际法中的国际法主体资格标准为基础，重点分析确立法国殖民制度的双边条约、1954年日内瓦协议及1973年《巴黎和平协定》等国际多边条约和文件，判断越南国际法主体资格的演变过程。本文认为，通过日内瓦协议，越南重新取得民族独立，此时尽管存在北越、南越两个政权，但越南仍为一个主权国家。此后，越南逐渐分裂为两个国家，北越代表越南民主共和国行使主权，越南南方的合法政府悬而未决。直至北越推翻南越，越南分离局面结束，统一后的越南是北越的人格延续。 越南统一前后的国际法主体资格与中越在南海的岛礁领土主权争端息息相关。南越曾对中国西沙群岛、南沙群岛提出非法主权主张，而北越明确承认西沙群岛、南沙群岛是中国的领土。由于统一后的越南是北越的延续，需要继续承担北越的国际法义务和责任。因此，在国家延续和禁止反言规则的双重作用下，今天的越南不能撤回或否认北越先前的承认，也不能依靠南越先前的主权主张，来证明越南对两群岛存在持续主权诉求。
After the Second World War, the rise of anti-colonial movements and the outbreak of the Cold War brought challenges to traditional international legal order. Against the background, on the territory of Vietnam, two political regimes existed at the same time, namely North Vietnam and South Vietnam. Being hostile to each other, they both claimed sovereignty on behalf of the entire Vietnamese people. By adopting opposing foreign policies, the two regimes received recognitions and supports from the Eastern Bloc and the Western Bloc respectively. After overthrowing South Vietnam in 1975, North Vietnam established a unified State—Socialist Republic of Vietnam in the following year. Vietnam’s struggle for national independence and unification lasted for a century. The French colonial administration and the existence of the two regimes thereafter raised the issue concerning the statehood of Vietnam. For example, whether Vietnam constantly remained unified as one single State? If so, which regime was entitled to represent Vietnam to exercise State activities? Since international personality is the starting point to determine rights and obligations under international law, the clarification of this issue is of practical importance. The period of time concerned in this thesis is from the 1860s to the 1970s, namely from the establishment of French colony to the final reunification of Vietnam. The methodology of positivism research is adopted. By referring to historical documents, the Vietnamese history of certain period is presented. Based on the criteria of statehood in general international law, the thesis pays special attention to the bilateral agreements on the establishment of French colony, the 1954 Geneva agreements and the 1973 Paris Peace Accords. It is submitted that Vietnam regained independence through Geneva agreements, when Vietnam still remained as one single State despite the existence of two regimes. Afterwards, Vietnam was gradually separated as two States. While North Vietnam legally represented Democratic Republic of Vietnam, the legal government of the southern part of Vietnam remained undecided. The overthrow of South Vietnam ended the separation of Vietnam. The unified Vietnam is the continuity of North Vietnam. The international personality of Vietnam is closely related to the territorial dispute between China and Vietnam in the South China Sea. While the South Vietnam raised unlawful claims to sovereignty over China’s Xisha Islands and Nansha Islands, North Vietnam explicitly recognized China’s sovereignty over these two Islands. As the continuity of North Vietnam, the unified Vietnam is obliged to undertake North Vietnam’s international commitments. Accordingly, due to the application of State continuity and estoppel, Vietnam is not allowed to withdraw or deny the recognition of North Vietnam, nor to demonstrate that Vietnam has raised continuing sovereign claims over Xisha Islands and Nansha Islands by referring to the activities of South Vietnam.
