The thread about law in Antarctica got me thinking, in a broad sense, which laws would most likely be applicable in the following situations? Yes I realize the reality is always extremely nuanced and complicated and in some cases there’s no clear answer while in others the situation is ridiculous enough that there’s simply no practical need to discuss it, but humor me.
[ul]
[li]The middle of the Pacific Ocean at least 100 miles from any nation’s shore.[/li][li]An American citizen flying on an Australian-owned jet 20,000 feet over Saudi Arabia[/li][li]An American citizen flying his personal aircraft over Saudi Arabia (assuming he hasn’t been shot down!)[/li][li]Burrowed deep underground (say 10,000 feet) below China.[/li][li]At the exact center of the Earth[/li][li]On the surface of the moon[/li][li]A British man, a Russian woman, and an Israeli Rabbi who get into a scuffle in Antarctica. Or on a ship in the Arctic circle?[/li][li]On a Canadian spaceship in geosynchronous orbit over Asia[/li][li]On the surface of Mars[/li][/ul]
Interesting questions. I’ll take a stab at some of them, although it’s only a guess as I’m certainly no expert in international law…
In the middle of the Pacific Ocean or on a ship in the Arctic Circle Authority would rest in the Captain of the vessel. Since no land-based laws apply, the captain of a ship on the high seas has near-total dictatorial powers.
On the Moon or Mars, or in space the ranking authority would likely be the captain of the mission, probably, again the captain of the ship that brought you there. His authority in turn would stem from mission control.
The passengers and crew of an airplane are under the jurisdiction of the land-based nation whose airspace they are occupying. Same thing if you’re burrowing underground.
The Englishman, the Russian and the rabbi in Antarctica would be a grand free-for-all…but my money’s on the Englishman.
The ranking authority at the center of the earth? dunno…God maybe?
The foregoing is a matter of guesswork & opinion…denials, rebuttals and alternative gueses are welcome
SS
I am quite sure that this is incorrect—The jurisdiction would be in the country where the airline was based in. (for example, a Quantas flight would be under Australian jurisdiction no matter what country it was flying over. However, if it was landed in a different country for a layover etc. jurisdiction may be different)
Yes, the laws of the flag of the vessel apply at sea.
The laws of jus cogens apply everywhere, to everyone. Treaty law applies everywhere to the signatories of the treaty. Nations have the ability to apply their laws to their own citizens wherever they are. Customary international law applies everywhere to every nation (and therefore to their citizens) that has not continuously and conspicuously objected to the customary law.
And nations have all kinds of ways to exert extra-territorial jurisdiction of varying types, especially for crimes against itself or its citizens. There are also things like the Alien Torts Claims Act, that can be used to create civil actions in the US for acts that occured in foreign countries. Long story short, it’s complicated 
and you’re usually, in theory if not in practice, subject to a lot more jurisdiction than you might guess.
As far as the plane goes, you would almost certainly be under both, to some extent.
I’m not an expert on outer space law by any means, but AFAIK, jurisdiction on Mars is governed by the 1967 Outer Space Treaty. If I understand the treaty correctly, then any ship on the surface of Mars (or persons from that ship) would be subject to the jurisdiction of the ship’s launching country or the country for which the ship would be under jurisdiction if it was on Earth.