unsign

Etymology

From un- + sign.

unsign means to remove one's signature from (something one has signed). Lexicurio rates it Rare gem — a strength score of 81 out of 100.

verb

To remove one's signature from (something one has signed).“Listen : I say we signed, and there's no unsigning. And the voyage is never completed, though some may ask What creature is this, with the sea through his eyes looking[?] […] We signed and there's no unsigning. Hell, no, but she rolls And she rolls us like foam from her flanks, the gay mulatto.”
To declare void one's signing of (a treaty).“Third, transnational legal process could be used to erode the force of the novel US tactic of unsigning the Rome Treaty.”