Both aspects of this case have attracted comment. The first (issue estoppel) is interesting because it gives rise to the possibility that when the court considers Yukos Capital's enforcement application in full, it will, on the basis of the issue estoppel, enforce the original arbitral award despite it having been annulled in the courts of the seat of arbitration (Russia). It is thought that this would be the first time the English courts would have enforced an arbitral award that had been annulled or set aside in the courts of the seat of arbitration.

On the second issue (act of state), the court's ruling is interesting as, following an examination of the previous authorities, it adopts a narrow approach to the application of the act of state principle. The court concluded that what it characterised as the "pure" act of state principle only applies to challenges to the validity of the act of state in question. In the earlier case of R (Yukos Oil Company) v FSA [2006] EWHC 2044 (Admin), the court had concluded that the act of state principle did apply where it was an essential part of the claimant's case that the corporate assets of Yukos had been wrongfully expropriated. In this case, however, based on many of the same factual allegations, the court rejected the act of state plea because the claimant's case required only that the court find, as a matter of fact, that "there was co-ordinated activity aimed at re-nationalising Yukos' assets which, in fact, involved the executive intervening in the judicial process". Whether or not that intervention was "valid", "invalid", "lawful" or "unlawful" was not something the court needed to decide.

This result suggests that when considering whether the act of state principle will apply, the nature of the remedy sought may in practice be more important than the nature of the alleged act(s) of state. It also suggests that an earlier finding that the act of state principle does apply in the context of one type of claim will not prevent the same factual allegations being raised with respect to a later claim, where the validity of the act of state is not at issue.

For more detail on this case, see Legal update, Act of state doctrine only applies to validity of foreign state's acts (High Court).