In RSE Holdings AG v Republic of Latvia (PCA Case No AA861), the Secretary-General of the Permanent Court of Arbitration (PCA) accepted a challenge under the UNCITRAL Arbitration Rules 1976 to the arbitrator appointed by the claimant in an Energy Charter Treaty (ECT) arbitration. The Secretary-General held that the arbitrator's extensive work as counsel in other ECT cases would give rise to justifiable doubts in the mind of a reasonable and informed third person as to their impartiality.