The first and second lists are of all the permanent judges of the International Court of Justice, the main judicial organ of the United Nations, first chronologically and then by seat.
The third list is a list of judges appointed ad hoc by a party to a proceeding before the Court pursuant to Article 31 of the Statute of the International Court of Justice.
There are no formal rules for the allocation of seats other than that no two judges may be nationals of the same country.
In practice, the five permanent members of the United Nations Security Council have each had a permanent seat on the Court, except on three occasions.
That convention was broken in 2018 when an Asian judge was elected to a seat previously occupied by judges from the Western Europe and others group.