Can someone please explain the jurisdiction of the International Court of Justice (ICJ). It appears that a particular country takes its orders on some issues and the same country says that ICJ has no jurisdiction over other issues. Please keep it simple as I have no law or political science background.
To answer this, I'm going to summarize the relevant Wikipedia page.
You're right that the ICJ has no binding authority to compel states to follow its rulings. Thus, there's two types of cases it decides:
- Cases where both countries consent. This includes:
- Cases where both sides agree to take their dispute to the ICJ and be bound by its ruling. This is somewhat like arbitration where the sides agree on what question(s) they will ask the judges, and that they will accept whatever the judges' decision is.
- Cases where the dispute involves an international treaty which both countries have signed and contains a provision which allows one of them to "force" the other into court. I put "force" in quotes, because the second country voluntarily signed the treaty which contained that clause, which means they now have to obey it (or renounce the treaty).
- Cases where the state in question has voluntarily accepted the jurisdiction of the ICJ for most or all situations.
- Addressing requests for non-binding advisory opinions.
- The UN (or elements thereof) can request an advisory opinion from the ICJ. This ruling is not binding on anyone, although it may provide grounds to bring the first kind of case.
TL;DR The ICJ has jurisdiction only if two states refer a matter to the court, or if a treaty (of course, one that is ratified by the parties) provides for jurisdiction. In practice, many countries opt out of (formally, "have reservation(s) against") such articles in treaty.
A country can also accept compulsory jurisdiction, but only against another state which does the same.
Finally, ICJ has the right to give advisory opinions (non-binding) at the request of some UN organizations.
For details, refer to the Statute of the ICJ:
The jurisdiction of the Court comprises all cases which the parties refer to it and all matters specially provided for in the Charter of the United Nations or in treaties and conventions in force.
The states parties to the present Statute may at any time declare that they recognize as compulsory ipso facto and without special agreement, in relation to any other state accepting the same obligation, the jurisdiction of the Court in all legal disputes concerning:
a. the interpretation of a treaty;
b. any question of international law;
c. the existence of any fact which, if established, would constitute a breach of an international obligation;
d. the nature or extent of the reparation to be made for the breach of an international obligation.
The declarations referred to above may be made unconditionally or on condition of reciprocity on the part of several or certain states, or for a certain time.
Such declarations shall be deposited with the Secretary-General of the United Nations, who shall transmit copies thereof to the parties to the Statute and to the Registrar of the Court.
Declarations made under Article 36 of the Statute of the Permanent Court of International Justice and which are still in force shall be deemed, as between the parties to the present Statute, to be acceptances of the compulsory jurisdiction of the International Court of Justice for the period which they still have to run and in accordance with their terms.
In the event of a dispute as to whether the Court has jurisdiction, the matter shall be settled by the decision of the Court.
The Court may give an advisory opinion on any legal question at the request of whatever body may be authorized by or in accordance with the Charter of the United Nations to make such a request.
Questions upon which the advisory opinion of the Court is asked shall be laid before the Court by means of a written request containing an exact statement of the question upon which an opinion is required, and accompanied by all documents likely to throw light upon the question.
Jurisdiction is based on consent. Countries agree (in different ways) to submit cases to the ICJ so it's perfectly possible for them to refuse its jurisdiction in some matters.
Some countries have issued a declaration agreeing in advance to the jurisdiction of the court (typically with some reservations) but all members can also submit a specific cases and some treaties also provide that disputes arising from the treaty should be resolved by the court.