Call Me A War Criminal

I'm reading a WWII book right now and just reminded me about why the Geneva Convention was signed: as a way to protect soldiers from torture and other terrible treatment by captors. It was not a humanitarian document, but had that effect. It was a contract. You treat ours okay and we'll treat yours okay. It was a simple deal.

Today, it is assumed the Geneva Convention applies irrespective of the situation and specifically comes up with respect to terrorists who not only haven't signed the Geneva Convention, but don't abide by the terms of the deal.

This isn't an argument for torture, but how in any way can one side of a contract be expected to honor it when the other side doesn't agree to it.

It's like a writer demanding he get paid for a script that he refuses to write. Does that make any sense?

UPDATE: Or, is the Geneva Convention more appropriately regarded as a self-restraint document...essentially an internal memorandum which identifies what we as a nation deem to be a moral and just way of behaving in times of war.