To consider and decide on costs in international arbitration is a relatively simple exercise. Not so in this case. The controversy between Claimant Tembec, Inc., Tembec Investments, Inc., and Tembec Industries, Inc. (together, “Tembec”) and Respondent United States of America (the “United States”) over the allocation of costs has consumed unusual amounts of time and energy, not only by the two parties but by the Tribunal as well.