Be sure to read Craig Murray’s article linked on the TAC front page, in which he explains what law applies to ships attacked by a national military in international waters. Here’s the nub of it:
There are … two clear legal possibilities.
Possibility one is that the Israeli commandos were acting on behalf of the government of Israel in killing the activists on the ships. In that case Israel is in a position of war with Turkey, and the act falls under international jurisdiction as a war crime.
Possibility two is that, if the killings were not authorised Israeli military action, they were acts of murder under Turkish jurisdiction. If Israel does not consider itself in a position of war with Turkey, then it must hand over the commandos involved for trial in Turkey under Turkish law.
In brief, if Israel and Turkey are not at war, then it is Turkish law which is applicable to what happened on the ship.
And yes, Turkey is a NATO member. Israel is not.