 A basic norm to explain the legal character of the Vienna Convention may be Article 38 of the Statute of the International Court of Justice, a treaty to which all member states of the UN must also be a party. But Article 38 is a treaty provision which, on first inspection, does no more than identify the applicable law in disputes brought before the Court. Applicable law clauses are far from infrequent in treaties that provide for judicial settlement of disputes, and their existence supports the non-systemic and episodic nature of international law. So in what way can Article 38 be said to be to embody the rule of recognition? Unlike other applicable law clauses, Article 38 has come to perform a systemic function, and is regularly relied upon by domestic as well as international courts. It is foundational at least in an explanatory sense, i.e., as a rule about how “primary rules may be conclusively ascertained, introduced, eliminated, varied” (Hart 1961 [2012: 94]).