Social media usage by States has increased exponentially in recent years. This phenomenon, known as “twiplomacy”, has become ubiquitous. Given that almost every State in the world now issues statements via social media, this article examines the potential for Twitter posts to form part of the “raw material” for the formation of customary international law. In other words, it considers whether customary international law can be “made”, or evidence of it identified, on social media. Public statements can, in the right contexts, act as State practice or as evidence of opinio juris, and a Twitter post from a State account ultimately is a public statement like any other. Based on an original scoping study, it is argued that there is evidence of statements being posted on Twitter that, were they issued in a more traditional context, would be seen as having the potential to constitute State practice or evidence of opinio juris. The study also suggests that such examples are not yet common, but it is predicted that they will become so. Therefore, this article goes on to examine a number of possible implications of twiplomacy for the identification of customary international law that must be considered, should social media indeed emerge as a notable breeding ground for new rules of custom. These implications include the blurring between the “personal” and the “official”; the brevity and (lack of) clarity and rigour of tweets; the significant increase in the amount of relevant data but also its comparative “centralisation” (with potentially positive as well as negative consequences); and concerns regarding authenticity. It ultimately is concluded that twiplomacy will not change the requirements for the formation of customary international law, but it is likely to have significant implications for how lawyers and researchers go about the practical process of identifying it.

中文翻译：

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Twiplomacy 的兴起和习惯国际法在社交媒体上的形成

近年来，各国对社交媒体的使用呈指数级增长。这种被称为“twiplomacy”的现象已经无处不在。鉴于世界上几乎每个国家现在都通过社交媒体发表声明，本文探讨了 Twitter 帖子成为习惯国际法形成“原材料”一部分的潜力。换言之，它考虑是否可以在社交媒体上“制定”习惯国际法，或识别出习惯国际法的证据。在适当的情况下，公开声明可以作为国家惯例或法律确信的证据，而来自国家账户的 Twitter 帖子最终是与任何其他公开声明一样的公开声明。根据最初的范围界定研究，有人认为有证据表明 Twitter 上发布的声明是在更传统的背景下发布的，将被视为有可能构成国家实践或法律确信的证据。该研究还表明，这样的例子还不常见，但预计它们会变得如此。因此，如果社交媒体确实成为新的习惯规则的显着滋生地，本文将继续研究 twiplomacy 对识别习惯国际法的一些可能影响，这些影响必须加以考虑。这些影响包括“个人”和“官方”之间的模糊；推文的简洁性和（缺乏）清晰性和严谨性；相关数据量显着增加，但其相对“集中化”（具有潜在的积极和消极后果）；以及对真实性的担忧。