It is illegal for a player to play so as to recreate a board position of the game, previously created by a play of the same player.

The British Go Association claims to use the same rules as the American Go Association

This document is inspired by the AGA's official statement of the rules and our interpretation of those rules.

So it seems they are actually using natural situational superko...

Right, this is the same in France with the FFG rules.

However, this is theory. The use of NSSK allows to immediately recapture in a ko if you passed one move before, and this is probably the only case where the difference between NSSK and PSK/SSK might be encoutered in a real game (certainly on a 9x9 board).

Not quite. They don't claim an exact copy:



Yes, as the authors of the AGA rules intended theirs too as well, but they were imprecise/misinterpreted.

Right, this is the same in France with the FFG rules.

However, this is theory. The use of NSSK allows to immediately recapture in a ko if you passed one move before, and this is probably the only case where the difference between NSSK and PSK/SSK might be encoutered in a real game (certainly on a 9x9 board).

In practice, it is extremely likely that the referee will refuse the application of the NSSK rule, arguing that it was "not the intention of the writers of the rule".



Here, with the NSSK rule, all stones are alive, including white's top group and black's A1 chain !!

White passes. If Black J9, then White J8 (absurd move allowed by the NSSK rule !). If Black plays anywhere else, White passes, ensuring that W J8 is always legal after B J9.
If White captures in B3, her top group dies. Black J9, and White J8 is now illegal because it recreates the situation already created by White B3. Therefore Black A1 lives.

As long as White passes, she doesn't create any situation on the board, and all of her subsequent moves are legal, including recapturing in a ko.

See discussion in viewtopic.php?f=45&t=11510

Except the BGA rules (http://www.britgo.org/files/rules/rulesofplay.pdf) have rule 6.1:

6.1 Ko
It is illegal for a player to capture a single stone which itself captured a single stone of the same player on the
previous move.

The use of NSSK allows to immediately recapture in a ko if you passed one move before