I think you stated it best yourself: "Declaring war is a complex question".
Besides declaring war, congress also has the ability to enact specific legislation for the conduct of the tribunals for the terrorists- that's what irritates me so about their criticism of Bush, they could enact law (do their job) instead of criticizing Bush for using the general guidelines in the UCMJ! But that would be doing something constructive!
(I suspect you'll have some debate on Bush's acting under the UCMJ- but let's save it for another thread.
I been shopping and it wears me to a frazzle :-)