Let's say a Canadian flies from New York to Tokyo on Korean Air and hacks the German tourist's computer seated in front of her while over the Pacific. Who's laws apply? (Canada, US, Japan, Korea, Germany?)
Apparently almost anybody's, including the French.
Firstly, there is Korea. While over "international waters", the registered country's law applies. Therefore, a 20 year old American can drink alcohol, because while the drinking age in America is 21, it's only 20 in Korea. The Korean's would get first stab at prosecuting
Secondly, there is the country of the victim. If the Koreans decline to prosecute this hacking case, then the Germans can, since it's the German tourist in our scenario who is the victim.
Thirdly, almost any country can under the principle of the "universal jurisdiction" against "international crimes". This means any country (such as the French, even though) can prosecute for a violation of international law like piracy or slave trading (but only as long as the Koreans decline to). This may or may not apply in this case, depending upon whether hacking is considered illegal by international law.
All this is only my guess based upon this article at FindLaw (h/t @KippiHax). The final admonition from that article is that international law is terribly complex and you need an expert to interpret this, so if you plan on hacking any German tourists over the Pacific, you should probably engage an attorney first.