Sentence:  Unsigning the Rome Statute. My happiest moment at State was personally “<WSD>unsigning</WSD>” the Rome Statute that created the International Criminal Court (ICC). ... bureaucrats urged at every turn that foreign governments would be extremely upset if we <WSD>unsigned</WSD>. In fact, only High Minded Europeans cared even slightly, which was simply further evidence that <WSD>unsigning</WSD> was the right thing to do. 
Meaning of the word marked with <WSD> tags:  To declare void one's signing of (a treaty).