the zettai ryoukai is the area between the socks and the skirt.
it's absolute territory because it is DEFINITELY a place you cannot enter without a peace treaty or intense negotiations beforehand
絶対領海に入ってほしいときは了解が必要だね。
Ah, Japanese polysemy... seriously, it's really funny how you need tens of thousands of ideograms to make sure you aren't mistaking stuff such as "me" with "you" (from kansai, with love), "green" with "blue" (only due to an archaism AFAIK, though) or other equally silly stuff. And don't even get me started on the ridiculous number of readings 上 has, for crying out loud.
Properly localizing characters such as Agasa from Conan that love cracking puns at every opportunity they get is such a pain...