I would ask, by what means does anyone have the rightful authority to command what another culture may eat/kill?
Suppose my neighbor comes to my house and tells me what to eat. I respond, "You have no authority over me!". He then says, "Ok...I'll be back."
He returns with another neighbor at his side. Both command, "You cannot eat whale!!"
I answer, "Neither you, nor your neighbor have authority over me! You can bring TEN neighbors, and if neither one individually have authority over me, then all of them COLLECTIVELY don't have authority over me either!"
So, no nation has authority over another. Nor does a group of nations (UNITED NATIONS) have rightful authority over Japan.