1998-11-30 last update, 1996-09-15 first day, Robert Jasiek
The Prohibition Rules aim with a precise text at easy determination of allowed moves, even if many kos are on the board. Kos may have so called single, double, or triple ko stones, unlike the Basic Ko Rules that know single ko stones only. Between so called ko threats outside all kos each player can play only once on each board point of all kos. The Prohibition Rules are illustrated with examples.
A ko consists of the marked board points in any of the following shapes, in any equivalent shape, in any equivalent shape with reversed colours, or in any such shape of which a part or parts - but not any marked board point - are cut off by at least one edge of the board. In any shape diagram not marked empty points may be of empty, black, or white colour as long as no illegal position arises.
basic ko : A single stone that has captured a single stone may not be recaptured immediately.
prohibition : From all board positions with the same set of board points of all kos and with the same configuration of stones on the board without the set each player may only once play on each board point.