Suppose the ICC has issued a warrant for my arrest (and that I may or may not be a head-of-state). Now suppose I embark on some maritime trip, which passes in international waters. Is it legal for a state party to the Rome statute to intercept my vessel, in international waters, place me under arrest and send me to the Hague?
If the answer is "it depends", please say what this depends on.
Note: This question is only about marine travel, not air travel.
If the ship's master gives permission for the boarding.
If your vessel has been ordered to stop while in national waters and you don’t and continue into international waters the vessel may be pursued and boarded.
If you are stopped by a warship of your ship’s nationality.
If your vessel is believed to be engaged in piracy, the slave trade, illegal broadcasting, or is without nationality.
One circumstance that would allow arrest is if the ship's flag is that of a country that has signed the Rome Statute. Then, you can be arrested immediately, as the law of that country applies on the ship. The captain has the right (if not even duty) to detain you.
As an example, the swiss law on high sea shipping (Seeschifffahrtsgesetz) states in Art 1:
Die Seeschifffahrt unter der Schweizer Flagge4 untersteht dem schweizerischen Recht, soweit dies mit den Grundsätzen des Völkerrechts vereinbar ist.
The shipping under Swiss flag is under Swiss Law, asfar as this is possible under public international law.
Later on, the law states that the captain has the power of the Police to investigate a crime on board the vessel or to detain a suspect. The law doesn't explicitly state that he has to execute an arrest warrant on a passenger, but I would guess that's just because that law isn't supposed to include all possible cases.
Other countries for certain have similar regulations, as this is one of the reasons ships must fly a flag. Most civil and criminal issues (except typically for customs issues, when the ship is in foreign ports) are handled according to that country's law.
