Fragmentation Can of Worms

I thought it might be interesting if we try to develop an inventory of circumstances in which WTO law conflicts with other international law, in the narrow meaning of "conflict".  That is, where are there specific circumstances in which an  obligation of WTO law requires or prohibits an act that is prohibited or required by other international law:  where one legal requirement prohibits an act which the other forbids.  (I know there are other definitions of "conflict," but I am interested in this type of strict conflict for now.)  Also, I would not consider it a conflict where one of the treaties or rules contains a safeguard or other exception that would result in deference to the other.  So, for example, if compliance with the Montreal Protocol would be permitted under Article XX, it ain't a conflict.