Many international tribunals allow for States to appoint ad hoc judges in cases involving that State and where no national of the State is a judge on the Court. It is often said that these judges (and judges of the nationlity of parties) vote in line with the State that has appointed them (or whose nationality they hold). This seems to be true in the majority of cases. However, it is worth nothing that (i) it is not true in all cases and (ii) in most cases the ad hoc judge votes together with the majority so it is perhaps not remarkable that they vote in favour of the appointing State.
However, this popular wisdom suggests that where there are two ad hoc judges appointed by opposing States in the case, the ad hoc judges will vote in opposite ways. This is probably true in the majority of cases, but it is not always true. This leads to my question:
In which cases before an international tribunal have ad hoc judges appointed by opposing States voted for the same result?
Obviously, I am including the International Court of Justice in the question but I would also include the International Tribunal for the Law of the Sea or any other tribunal in which opposing States can appoint ad hoc judges. I would also be prepared to accept as within the scope of my question cases in which an ad hoc judge appointed by one party voted for the same result as a judge of the nationality of the other party. Or even cases where judges that have the nationalities of opposing parties vote for the same result.
I realise that “voted for the same result” is a bit ambiguous. What I mean is that both ad hoc (or national) judges wanted the same outcome from the judgment. However, I don’t mean that both of them simply voted against the judgment because neither particularly liked it, though for different reasons. Also, in cases where the tribunal’s dispositif may include several points, it is possible for ad hoc judges to agree on some of the minor points. What I really want to know is whether on core issues, the ad hoc judges have agreed.
I also have a follow up or bonus question:
Have ad hoc judges appointed by opposing States ever written a joint opinion with each other?