The Kingdom of Spain opposes Petitioners' Motion for Substitution (ECF No. 56). Under Federal Rule of Procedure 25(c), substitution is permissive and left to the Court's discretion. Courts permit substitution when it promotes the efficient resolution of the dispute. The proposed substitution offers no gain in efficiency. Spain's motion to dismiss is fully briefed and ripe for decision. The Court should exercise its discretion to deny the Motion for Substitution and allow this case to resolve between the proper parties.