The illegal moves in Carlsen-Inarkiev In the first round of the World Blitz Championship in Riyadh. Magnus Carlsen played Ernesto Inarkiev and the game ended strangely.
[FEN &quot;&quot;]
[StartPly &quot;53&quot;]
[Event &quot;World Blitz Championship&quot;]
[Site &quot;Riyadh KSA&quot;]
[Date &quot;2017-12-29&quot;]
[Round &quot;1&quot;]
[White &quot;Magnus Carlsen&quot;]
[Black &quot;Ernesto Inarkiev&quot;]
[Result &quot;1-0&quot;]

1. e4 c5 2. a3 Nc6 3. b4 cxb4 4. axb4 Nxb4 5. d4 d5 6. c3 Nc6 7. exd5 Qxd5 8. Na3 Bf5 9. Nb5 Rc8 10. Nxa7 Nxa7 11. Rxa7 e5 12. Nf3 exd4 13. Nxd4 Bd7 14. Nb5 Qxd1+ 15. Kxd1 Bc6 16. Bd3 Bc5 17. Re1+ Ne7 18. Ba3 Bxa3 19. Rxa3 Rd8 20. Nd4 Kd7 21. Ra7 Rhe8 22. Kc2 Kc7 23. Rb1 Rb8 24. f3 Nd5 25. Nxc6 Kxc6 26. Bb5+ Kb6 27. Rxb7+ Ne3+?? {An illegal move by Inarkiev; he leaves his King in check} 28. Kd3?! {Carlsen plays on; Inarkiev now calls an arbiter}

As can be seen above, after Carlsen played 27 Rxb7+, Inarkiev made the illegal move 27...Ne3+, leaving his own king in check. At this point Carlsen could have claimed a win because of an illegal move, however, he played 28 Kd3.   At this point Inarkiev called an arbiter and claimed a win because Carlsen made an illegal move.
As far as I read the arbiter first ruled in favor of Inarkiev. Later it was offered to continue the game from the position before the illegal move on the board, i.e. after 28. Kd3 (which was lost for black), which Inarkiev declined, after which Carlsen was declared the winner.
What rules (if any) cover a situation like this?
Also I've seen claims that Inarkiev has pulled this &quot;trick&quot; before. If true, when and where was that?
What rules (if any) cover a situation like this?


3.10.2 of the FIDE Laws of Chess defines when a move is illegal -


  3.10.2 A move is illegal when it fails to meet the relevant requirements of Articles 3.1 – 3.9


Articles 3.1 - 3.9 basically describe the moves of the pieces. Inarkiev's move was illegal because it breached 3.9.2 -


  3.9.2 No piece can be moved that will either expose the king of the same colour to check or leave that king in check.


3.10.3 defines when a position is illegal -


  3.10.3 A position is illegal when it cannot have been reached by any series of legal moves.


After Inarkiev made his illegal move the position was illegal because his king was in check and it was not his turn. After Carlsen made his (perfectly legal) move the position was legal again because Inarkiev was in check and it was Inarkiev's turn. Inarkiev was wrong to stop the clocks and claim an illegal move. The first arbiter made a mistake. Presumably Inarkiev said that Carlsen had made an illegal move and the arbiter took his word for it without checking - very unprofessional.

Article 7.5.1 defines when an illegal move has been completed (different from "made") and what should happen next in standard play games -


  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.


The same definition for the completion of an illegal move applies to rapid and blitz however the way the illegal move is handled is different unless certain strict conditions apply.

In blitz illegal moves are handled like this (i.e. "Competition Rules apply") only if -


  B.3.1 The Competition Rules shall apply if:
  B.3.1.1 one arbiter supervises one game and
  B.3.1.2 each game is recorded by the arbiter or his assistant and, if possible, by electronic means.


With 69 games they would need 69 or more arbiters. I don't believe they had that so according to B.4 Rapid rules apply -


  B.4 Otherwise, play shall be governed by the Rapid chess Laws as in
  Article A.2 and A.4.


The relevant article is A.4.2 -


  A.4.2 If the arbiter observes an illegal move has been completed, he
  shall declare the game lost by the player, provided the opponent has
  not made his next move. If the arbiter does not intervene, the
  opponent is entitled to claim a win, provided the opponent has not
  made his next move. 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. If the opponent does not claim and the arbiter
  does not intervene, the illegal move shall stand and the game shall
  continue. Once the opponent has made his next move, an illegal move
  cannot be corrected unless this is agreed by the players without
  intervention of the arbiter.


So, the sequence of events was -


Inarkiev makes an illegal move   
Neither the arbiter nor Carlsen spots it and Carlsen makes a legal move.   
Inarkiev incorrectly tries to claim the game.   
The arbiter who deals with it incorrectly believes Inarkiev without checking and awards the game to Inarkiev.   
The Chief Arbiter correctly overturns the decision and rules that Inarkiev must make a move in the position in which he made his incorrect claim.   


I don't know if the Chief Arbiter did this but in his position I would also award Carlsen an extra minute on the clock in accordance with article B.2.


  B.2 The penalties mentioned in Articles 7 and 9 of the Competition
  Rules shall be one minute instead of two minutes.


EDIT: Checking on the FIDE web site I see that they have published the regulations for the World Rapid and Blitz Championships which confirm that Rapid rules apply in the case of illegal moves -


  6.14 Tournaments will be played according to the rules of the inadequate supervision of the Rapid play Laws of Chess (FIDE Handbook,
  E.I.01B Appendices, art. 1 to 4). In addition, if a player displaces
  the pieces during the game: for the first time he receives a warning
  but for the second time he will be forfeited.


EDIT2: Perhaps I should just also point out for anyone reading this after 1st Jan 2018 that FIDE are unhappy with the "one illegal move loses in rapid and blitz" rule and this is changing from 1st Jan 2018. The new rules have a new article A.4.2 -


  A.4.2
  
  If the arbiter observes an action taken under Article 7.5.1, 7.5.2,
  7.5.3 or 7.5.4, he shall act according to Article 7.5.5, provided the opponent has not made his next move. If the arbiter does not
  intervene, the opponent is entitled to claim, provided the opponent
  has not made his next move. If the opponent does not claim and the
  arbiter does not intervene, the illegal move shall stand and the game
  shall continue. Once the opponent has made his next move, an illegal
  move cannot be corrected unless this is agreed by the players without
  intervention of the arbiter.


This basically says that in the case of an illegal move in "unsupervised" rapid and blitz the rules regarding when an illegal move is spotted and handled remain the same (if neither the players nor the arbiter spot it and stop the game then the game continues) but the penalties are as in standard play with a time penalty and restored position in case of a first offence and losing the game in case of a second offense.