On 12 December the House of Lords delivered its long-awaited judgment in Al-Jeddah, which is to do with the application of the ECHR to a person detained in a UK detention facility in Iraq. One of the issues concerned the scope of Article 103 of the UN Charter (which states that UN obligations override all other agreements). The HL held that this provision applies not only to UN obligations but also to UN authorizations.
This has direct relevance to Article XXI(c) GATT, which allows 'any action in pursuance of [a WTO Member's] obligations under the United Nations Charter for the maintenance of international peace and security.' According to the HL reasoning, this provision would now be triggered by a UN sanction that merely authorizes trade sanctions - as most do.
Two other points. If this question arose in WTO dispute settlement proceedings, a WTO panel/AB would need to decide it, as a necessary interpretation of a WTO provision. But doing this would also be 'determining rights and obligations outside of the covered agreements', which the AB said in Soft Drinks (para 56) that it would not do. This indicates that the AB's statement in this case might be in need of some refining. Second, this case provides further support for the argument (put forcefully by Joost) that, in terms of treaty conflicts, rights can conflict with obligations, though with the interesting spin that the term 'obligation' is interpreted also to mean 'right'.