Here's another GATT Article XX issue in the China - Exportation of Raw Materials case: the role of "sovereignty" in interpreting Article XX. With the caveat that this is just the complainants' characterization of China's argument, and I haven't seen China's actual submission, this appears to be a broad argument under GATT Article XX:
85. China devotes a great deal of time and effort to underscoring China’s belief that its economic justification – that is, a purported right to adopt measures regarding the use of natural resources to pursue domestic economic policies regardless of WTO obligations – is somehow reflected in Article XX(g). China characterizes this as an issue of “sovereignty” over its natural resources, and also purports to find support in the principles of “conservation” and “sustainable development.”
86. The sovereignty of a WTO Member over its natural resources is not at issue under Article XX(g). Neither is the right of a WTO Member to choose its economic policies at issue under Article XX(g).
87. Instead, what is at issue under Article XX(g) is whether a measure that is otherwise inconsistent with the GATT 1994 fits within the plain terms of the Article XX(g) exception: that is, whether it (1) relates to the conservation of an exhaustible natural resource; (2) is made effective in conjunction with domestic restrictions on production or consumption; and (3) is not applied in a manner which would constitute a means of arbitrary or unjustifiable discrimination or a disguised restriction on international trade.
To what extent can general principles to which everyone subscribes, at least to some extent, such as sovereignty (or even "precaution"), be used to influence the interpretation of specific terms of an agreement?