Temporal and Material Scope of Self-Defence short of Armed Conflict

2022 Fiscal Year Final Research Report

• Project/Area Number: 18K12647
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 05030:International law-related
• Research Institution: Kobe City University of Foreign Studies (2020-2022); Sophia University (2018-2019)
• Principal Investigator: Hiromi Masayuki 神戸市外国語大学, 外国語学部, 准教授 (20707541)
• Project Period (FY): 2018-04-01 – 2023-03-31
• Keywords: 自衛権 / 安全保障法 / 武力紛争法 / 国連平和維持活動

Outline of Final Research Achievements

Under contemporary international law, even if a State exercises the right of self-defence, that does not necessarily mean that an international armed conflict thereby occurs, if such self-defence is exercised against a single armed attack. The content of the principles of necessity and proportionality of self-defence may vary according to the two concepts of "an armed attack", i.e. a single armed attack and a series of armed attacks. In the former case in which an armed conflict does not occur, the principle of necessity in the material sense, i.e. no alternative measures other than use of force, and the quantitative proportionality, i.e. proportionality between an armed attack and the responsive use of force in self-defence applies. In the latter case, the principle of necessity in the temporal sense, i.e. temporal proximity between an armed attack and the responsive use of force, and the qualitative proportionality, i.e. proportionality between aim and end, should be satisfied.

Free Research Field

国際法学

Academic Significance and Societal Importance of the Research Achievements

従来、自衛権行使における武力行使は、必然的に国際的武力紛争を発生させるとみなされてきた。これに対し、本研究では、実際にイラン・イラク戦争の最中に米国がイランに対して行使した自衛権を素材として、単発の武力攻撃に対する自衛権行使の場合、必ずしも国際的武力紛争が発生しない、あるいは武力紛争当事国とならないことを示した点に学術的・社会的意義があると考える。
また、自衛権の必要性・均衡性原則の内容については、これまで学説上対立があったところ、その対立を、単発の武力攻撃と継続的な武力攻撃との場合分けに応じて、必要性・均衡性原則が使い分けられるという理論構築を行ったにも意義があると考える。