In Perenco Ecuador Limited v Republic of Ecuador and Empresa Estatal Petroleos del Ecuador (ICSID Case No ARB/08/16), the challenge was based on comments made by one of the arbitrators in an interview. Although the arbitrator did not refer specifically to the parties or the arbitration, the Secretary-General of the Permanent Court of Arbitration applied the "appearance of bias" test in the IBA Guidelines and held that a reasonable third person would find that the comments gave rise to justifiable doubts as to the arbitrator's impartiality or independence. Read more.

In Participaciones Inversiones Portuarias SARL v Gabonese Republic (ICSID Case No ARB/08/17), the challenge was made on the grounds that one of the arbitrators had been the president of a tribunal in another ICSID arbitration against the same respondent, raising similar legal issues, which gave rise to a risk of prejudice. The challenge was decided by the Chairman of ICSID's Administrative Council, as the two remaining members of the tribunal were in deadlock. Applying the ICSID Convention, the challenge was rejected. Read more.

In Cemex Caracas Investments BV and another v Bolivarian Republic of Venezuela (ICSID Case No ARB/08/15), the tribunal had to decide whether a challenge by Venezuela to one of the arbitrators had been brought "promptly", as required by ICSID Arbitration Rule 9(1). It held that the challenge had not been brought in time and that Venezuela had therefore waived its right to object. Read more.