This is lift.Lift does
not mean "upwards force". It's a force borne from "a fluid flowing past the surface of a body." Angling the rocket upwards does not mean the rocket motor generates lift. Lift in this sense can also be provided by things such as helicopter blades (and actually anything - just only effectively by helicopter blades and the like), but fixed wings -
fins - are explicitly banned as a primary method of generating this lift.
If they're using fins, those fins are the primary source of generating lift.
EDIT: Furthermore,
in addition to our substantial technical backing, we also have this lovely clause of Article V to work off of:
The reason is that the imprecise nature of bombing results in unacceptable amounts of collateral damage against civilian objects, and such vehicles do not permit chance for military personnel to surrender during combat.
So not only are their finned rockets technically illegal, but they're also immorally illegal. Every word of the quoted sentence applies to Toskesh's rockets.
Toskesh proved in prior cases that morale arguments have a weight with UN. We have both technical and morale arguments.
And it's painfully obvious that we have enough of a case so even if they don't rule in our favor, it won't be seen as a frivolous appeal. Even if they rule against us, it'll still generate important (dangerous) precedent and the U.N. knows that. We don't actually have any substantial risk towards arguing that their rockets are illegal.