The unwritten nature of customary international law (CIL) enables it to remain flexible and easily adaptable to changes in States practice and opinio juris, but at the same time may be the source of substantial uncertainties when it comes to the formation, identification and development of customary norms. To investigate this issue, this paper examines the attitudes adopted by States in the aftermath of the airstrikes conducted in Syria by the USA, the UK and France in 2017 and 2018, respectively. The paper is divided into two parts: the first part includes a brief summary of the statements made by States, including the intervening States, after the 2017 and 2018 airstrikes, while the second part is devoted to the analysis of how CIL may have been influenced by the reaction of States to the airstrikes.

国际习惯法（不成文的性质CIL），使其能够保持灵活和容易适应各国实践和变化的法律意见，但在同一时间，当涉及到的形成，识别和发展可能是很大的不确定性的来源习惯规范。为了调查该问题，本文研究了美国，英国和法国分别于2017年和2018年在叙利亚进行空袭后各国采取的态度。该文件分为两个部分：第一部分包括2017年和2018年空袭后各国（包括干预国）的发言的简要摘要，而第二部分专门分析了CIL的方式 可能受到各国对空袭反应的影响。