Supposedly the United Nations.
World Trade Organisation
Mediator
The Supreme Court settles the disputes in connection with the election of the vice president and the president . Its verdict is final.
League of Nations
The Supreme Court
Executive branch
Resolving international trade disputes.
United Nations
World Trade Organization through its dispute settlement procedures.
The Supreme Court of India
The World Trade Organization helps resolve trade disputes between member states. It acts as a forum for the dispute to be presented, conducts an investigation and provides a ruling.
As best as I can tell, the Supreme Court, which is a federal court, settles disputes between neighboring states.