Is arbitral investment case-law on expropriation precedential in a legally relevant sense? Orthodox approaches are marked by agreement on a narrow set of arguments, namely that international law is not a common law and arbitral awards do not have stare decisis power, that jurisprudence is hugely important and tribunals rely on it, and that there must therefore be a sort of de facto system of precedents in operation. In effect, ‘factual importance’ is fashioned into a source of legal authority. However, few arguments are given as to why this transfer from fact to law would occur and they do not provide a foundation for a general legal value for precedents. Yet the weight of arbitral jurisprudence is both too great to ignore and too helpful in discovering what ‘’ means in a pragmatic sense. Precedents are statements about general norms; outside the common law, judge-made law is merely an interpretation of a general norm in a judgment. Not even a constant tradition of decisions can turn such a statement into a norm.