A specific and attainable goal. Not easy, perhaps not even likely, given the precedent that would be set - but not impossible. Sufficient political pressure will have an impact.
Now the focus should be directed at that one goal, that one demand. It is a clear, concise, articulated definition of victory and set of parameters for the Mission. It is not only a moral and just goal - it is a PR win.
Remember your Churchill: If you have an important point to make, don't try to be subtle or clever. Use a pile driver. Hit the point once. Then come back and hit it again. Then hit it a third time - a tremendous whack.
Free the Hammonds!