In CMS Gas Transmission Company v Argentina (ICSID Case No ARB/01/8), an ad hoc committee has annulled those parts of the tribunal's award in which it held that there had been a breach of the umbrella clause in the US-Argentina BIT, but has upheld the remainder of the award.

The decision of the ad hoc committee provides a clear illustration of the distinction between appeals on points of law, and annulment on the basis of manifest excess of power. In this case, the committee took the view that the tribunal's award was wrong in law, but that this was insufficient to justify annulment.