A move that returns to a previous board position is illegal, AFAIK.<p><a href="http:&#x2F;&#x2F;senseis.xmp.net&#x2F;?TrompTaylorRules" rel="nofollow">http:&#x2F;&#x2F;senseis.xmp.net&#x2F;?TrompTaylorRules</a> :
6. A turn is either a pass; or a move that doesn&#x27;t repeat an earlier grid coloring