As Fonzie indicates, ethically, not without the approval of probably both parties. However, UDRP is not true "legal" cases, but a method of arbitration. The law of the country of one or both parties to a dispute may apply to complicate things.
If you have a problem with it, definitely make the point before the arbitration goes forward. Better to have it fixed before than have one party tempted to sue in a more expensive court if they later decide it was an unfair decision.