Since the siege lasted after Hawkwing's death, that would be impossible. In PoD, Egwene says that the last object of a declaration of war was Hawkwing himself. Even if the Law of War was put on the books in order to deal with him, the phrasing argues otherwise. That would make him the "only" one on whom war was declared, not the "last." Indeed, the irregular expansion of the Tower's territory in the FY period from its symetrical boundary of the AB era suggests the Tower was right in the middle of international affairs and politics, playing hardball like anyone else, and likely declared war as they found it convenient or necessary. The era when they held political supremacy and rulers were crowned by the Tower's leave is always stated as the days "before the Trolloc Wars" implying their time as nuetral or transcending such practices had long since passed by Hawkwing's day.

While its uncommon use would explain Siuan's pique at being restrained by the Hall in tGH, in fact the law is much older. It is two thousand years old by this time.

I doubt it. On reflection, given Romanda's ready use of the law to restrict Egwene (and she was not in the Hall that cast that vote regarding Siuan), it is doubtful that the two provisions are so closely linked. Otherwise, Romanda's (and indeed all the Sitters)missing the obvious benefits to Egwene in a declaration of war becomes inexplicable. Rather the dating of the restriction on the Amyrlin's safety suggests that the Law of War is much, much older, and very much on the minds of the Sitters and sisters of the time when the safety law was made, that they thought to place that exception in it. This too, might suggest a reason for declaring War on the Shadow. While there are issues of power and authority, there ARE wartime practices that may be necessary. Can Egwene do all that she needs to from a desk? Or will she be satisfied with asking the Hall's permission to go about as Tarmon Gaidon draws closer and the number of places that do not fall under the description of "danger" dwindle? The reason for an official war being the exception to the Amyrlin-safety law is the necessity of streamlined measures.

And there will be issues of whether or not a declaration of war is necessary to deal with such an issue, with Egwene's seizure of dictatorial powers rubbing the Sitters raw, the obvious inability of the Tower to match the Seanchan in direct fighting capability (thus suggesting other courses of action than open war to be in their best interest - such as applying political and economic pressure, fighting through proxies and a war of intrigue and assassinations such as the Bloodknives will likely inspire), and Egwene's mishap which resulted in her capture. Lacking our narrative perspective, I doubt the Aes Sedai will see the last as a key step in the Pattern's plan or something crucial and necessary to her gaining the trust of the loyalists, and rather as a potential disaster for Egwene averted solely by Elaida's fortuitous arrogance (I foresee a great deal of whitewashing over the exact nature of events during the rebellion, with the blame for as much as possible or credible being placed on Elaida's doorstep).

To which I agree, so a declaration will probably not be necessary.