First of all, I don't think this is a duplicate of what happens on the first illegal move in a game. This is what happens after the second if the first is unclaimed.
The setting is a tournament under FIDE rules (2018).
Can a win be claimed after the second completed illegal move completed by one side, if neither player nor the arbiter intervened upon the completion of the first?
Assume the arbiter was summoned by the claiming player, and sees the game and its score for the first time. Assume that both players recorded the moves faithfully, illegalities included, such that they agree on the history of events and that there is no doubt that more than one illegal move was completed. (See below for an example.)
The relevant articles of the FIDE Laws of Chess seem to be:
7.5.1 An illegal move is completed once the player has pressed his clock. If during a game it is found that an illegal move has been completed, the position immediately before the irregularity shall be reinstated. If the position immediately before the irregularity cannot be determined, the game shall continue from the last identifiable position prior to the irregularity. Articles 4.3 and 4.7 apply to the move replacing the illegal move. The game shall then continue from this reinstated position.
7.5.5 After the action taken under Article 7.5.1, 7.5.2, 7.5.3 or 7.5.4 for the first completed illegal move by a player, the arbiter shall give two minutes extra time to his opponent; for the second completed illegal move by the same player the arbiter shall declare the game lost by this player. However, the game is drawn if the position is such that the opponent cannot checkmate the player’s king by any possible series of legal moves.
As a concrete example, look at the following game and assume the arbiter was summoned after the move 24. 0-0-0. Both players recorded the game and agree the game score is correct.
[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1 "] 1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6 4. Nc3 Bb4 5. Bxc6 bxc6 6. d4 exd4 7. Nxd4 Ba6 8. O-O d5 9. exd5 cxd5 10. Re1+ Ne4 11. Qg4 Qf6 12. Bg5 Qg6 13. Qf4 O-O-O 14. Bxd8 Rxd8 15. f3 Nxc3 16. bxc3 Bxc3 17. Reb1 Bxa1 18. Rxa1 Kd7 19. Qf5+ Ke8 20. Qxg6 hxg6 21. Nc6 Ra8 22. Kf2 O-O-O 23. Ke1 Re8+ 24. O-O-O
(Aside: this is probably a plausible game between weak players, so the question has maybe more than academic value.)
The illegal moves are
24.0-0-0. (Relevant articles of the Laws: 22.214.171.124.1 for the first three, 3.9.1 for the last.)
- Black attempts to claim a win under 7.5.5. Does this stand?
- Could white have claimed a win had she summoned the arbiter after
- Extension: if the claimed win(s) does (do) not stand, under 7.5.1, from which position does the game resume?