Dave Bell I think that definitely puts some limits on how much you can ignore the Convention if Al Qaeda or Afghanistan are not "High Contracting Parties".

-- nope. The rules apply only to the contracting parties vs. a vs. each other; they're mutual concessions and confer no "human rights" on individuals.

At the broadest plausible interpretation, they could apply to a side which _explicitly accepts_ the Conventions and which _in practice makes a good-faith effort to abide by them_.

Since neither of those conditions is applicable to the Taliban or al Qaeda and their ilk, the Conventions are simply irrelevant. We're under no restrain but our own unilateral will here.