Answers.Body: <p>It is never, <em>ever</em> legal to move into check. Period. No ifs, no buts. No exceptions whatsoever.</p>
  
  <p>That's the best way to think about it, since it gives the least scope for confusion. If you want to think of it in terms of capturing the king ending the game, look at it this way: if you move into check, your opponent can capture your king, which immediately ends the game. It's irrelevant if your opponent's capture caused him to move into check too: you can't retaliate by capturing his king because the game already ended.</p>
  
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Answers.Text: It may also be useful to recognize the difference between the rules involving check, versus a rule that says that a player whose king is captured loses: a player who has any move available that does not put the king in *immediate* danger must play such a move, but if all of a player's moves would place the king in immediate danger when it isn't already, the game ends without the player being obliged to put the king in danger.
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Answers.UserDisplayName: David Richerby
Answers.Body: <p>No. Check is check, even if the checking piece cannot legally move. There is extensive discussion of this in the answers to the question <a href="https://chess.stackexchange.com/questions/2348/illegal-move-can-put-a-king-in-check?rq=1">illegal (?) move can put a king in check?</a>. </p>
  
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Answers.Text: But can the player who moved his king into check make an illegal move?
Answers.UserDisplayName: G Foster
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Answers.Text: I don't understand your question. Can you update the original question with an explicit example?
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Answers.UserDisplayName: dfan
Answers.Body: <p>I'd rather be more cautious and answer this question taking into account the time control used in the game because, as you will see, there are some concessions that regulations grant when the players have less time to think.</p>
  
  <h2>If each player’s thinking time is at least 60 minutes:</h2>
  
  <p>The move in question is indeed illegal, as others have commented. End of story. Even though nobody notices the irregularity for a while, as the rules indicate (emphasis mine):</p>
  
  <p>7.5.1 An illegal move is completed once the player has pressed his clock. <strong>If during a game it is found that an illegal move has been completed, the position immediately before the irregularity shall be reinstated.</strong> 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.</p>
  
  <p><em>End of story</em>?</p>
  
  <p>There might be a rare exception in case the game has ended (by checkmate or resignation) without the mutual check (or any other irregularity) being noticed, and the players have signed their scoresheets. I am not sure what happens if the illegal move is noticed after that because:</p>
  
  <p>5.1.1 The game is won by the player who has checkmated his opponent’s king. This immediately ends the game, provided that the move producing the checkmate position was in accordance with Article 3 and Articles 4.2 – 4.7.</p>
  
  <p>5.1.2 The game is won by the player whose opponent declares he resigns. This immediately ends the game.</p>
  
  <h2>Rapid chess</h2>
  
  <p>When all the moves must be completed in a fixed time of more than 10 minutes but less than 60 minutes for each player; or the time allotted plus 60 times any increment is of more than 10 minutes but less than 60 minutes for each player.</p>
  
  <p>In my opinion, the problem is more clearly described in other questions  (both marked as a duplicate of this one):</p>
  
  <p><a href="https://chess.stackexchange.com/questions/22395/is-it-legal-for-a-move-to-put-both-sides-in-check">Is it legal for a move to put both sides in check?</a></p>
  
  <p><a href="https://chess.stackexchange.com/questions/21493/simultaneous-check">Simultaneous check</a></p>
  
  <p>Surprisingly, <strong>the rules specifically mention the situation of a mutual check:</strong></p>
  
  <p>A.4.4 <strong>If the arbiter observes both kings are in check</strong>, or a pawn on the rank furthest from its starting position, <strong>he shall wait until the next move is completed.</strong> Then, if an illegal position is still on the board, he shall declare the game drawn.</p>
  
  <p>Otherwise, it is understood that the game can continue. For reference: A position is illegal when it cannot have been reached by any series of legal moves. (article 3.10.3)</p>
  
  <p>Now, if this actually happens in a real game, the use of the word illegal to describe the move after the game has ended is arguable, because the move was illegal at its time, but now it is part of a legal game supported by the rules!</p>
  
  <p>For other irregularities, the procedure is similar:</p>
  
  <p>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, <strong>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.</strong></p>
  
  <p>To be completely precise, these Rapid rules do not apply if certain conditions are met. According to A.3.1, the Competition Rules shall apply to Rapid chess (i.e. the illegal move cannot stand) if:</p>
  
  <p>A.3.1.1 one arbiter supervises at most three games and</p>
  
  <p>A.3.1.2 each game is recorded by the arbiter or his assistant and, if possible, by electronic means.</p>
  
  <p>Otherwise, the Rapid chess rules do apply and the illegal move has a chance to stand.</p>
  
  <p>Finally, I have to mention that these Rapid chess rules <strong>also apply to Blitz</strong>, when all the moves must be completed in a fixed time of 10 minutes or less for each player (or the allotted time plus 60 times any increment is 10 minutes or less).</p>
  
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Answers.CreationDate: 2018-08-31T09:11:18.900Z
Answers.Text: I think this answer misses the point: in all cases it **is** illegal to put one's king in check, and that's clearly what the OP was asking about. What happens *after* an illegal move is played indeed depends on the time control, but that's a bit off-topic here and might cause even more confusion for the OP.
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Answers.Text: I thought it should be relevant because the rules specifically mention the OP's question. And the OP should know that if their opponent makes an illegal move in blitz **and** the OP does not notice the irregularity, it may stand.
Answers.UserDisplayName: Daniel Alfredo Sottile
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Answers.UserDisplayName: Daniel Alfredo Sottile
Body: <p>Can a player move their king into check if the opponents piece that is able to take king, is putting opponents king in check?</p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2015-01-07T20:23:48.057Z
Comments.Text: In other words, Can a rook that is between it's king and opponents queen be identified as a piece that cannot be moved and allow opponents king to be moved into rooks path? Or is this a case where a king cannot move into check?
Comments.UserDisplayName: G Foster
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2015-01-07T21:16:01.397Z
Comments.Text: I don't think the player can move his king into a check position in the first place. Is this an illegal move?
Comments.UserDisplayName: G Foster
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2015-01-07T21:17:29.147Z
Comments.Text: I think you will have to make an actual diagram with moves for this question to be clear.
Comments.UserDisplayName: dfan
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2015-01-07T21:19:55.473Z
Comments.Text: player 1 moves his queen to put player 2 in check.
Comments.UserDisplayName: G Foster
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2015-01-07T21:27:57.923Z
Comments.Text: player 1 moves his queen to put player 2 in check. Player 2 moves his rook just in front of his king to block player 1 queen. Player 2's rook is protected by his king (ie rook is next to king) Player 1 then moves his king into path of player 2's rook putting player 1's king in check. Can player 1 put his king into check or is this an illegal move?
Comments.UserDisplayName: G Foster
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2015-01-07T21:31:42.683Z
Comments.Text: That move would be illegal. As my answer states, it is illegal for Player 1 to make a move such that his king is in check, even if the checking piece cannot move. See the linked question in my answer for a more thorough discussion.
Comments.UserDisplayName: dfan
Tags: <rules><illegal-move>
Title: Moving king into check
ThreadText: # Moving king into check
  
  (Asked by: username_0 on 2015-01-07)
  
  Can a player move their king into check if the opponents piece that is able to take king, is putting opponents king in check?
  
  **Tags:** rules, illegal-move
  
  > **Comments:**
  > **username_0**: In other words, Can a rook that is between it's king and opponents queen be identified as a piece that cannot be moved and allow opponents king to be moved into rooks path? Or is this a case where a king cannot move into check?  
  > **username_0**: I don't think the player can move his king into a check position in the first place. Is this an illegal move?  
  > **username_1**: I think you will have to make an actual diagram with moves for this question to be clear.  
  > **username_0**: player 1 moves his queen to put player 2 in check.  
  > **username_0**: player 1 moves his queen to put player 2 in check. Player 2 moves his rook just in front of his king to block player 1 queen. Player 2's rook is protected by his king (ie rook is next to king) Player 1 then moves his king into path of player 2's rook putting player 1's king in check. Can player 1 put his king into check or is this an illegal move?  
  > **username_1**: That move would be illegal. As my answer states, it is illegal for Player 1 to make a move such that his king is in check, even if the checking piece cannot move. See the linked question in my answer for a more thorough discussion.  
  
  ---
  
  ## 3 answers
  
  ### Answer by username_2 on 2015-01-08. Score: 7
  
  It is never, *ever* legal to move into check. Period. No ifs, no buts. No exceptions whatsoever.
  
  That's the best way to think about it, since it gives the least scope for confusion. If you want to think of it in terms of capturing the king ending the game, look at it this way: if you move into check, your opponent can capture your king, which immediately ends the game. It's irrelevant if your opponent's capture caused him to move into check too: you can't retaliate by capturing his king because the game already ended.
  
  > **Comments:**
  > **username_3**: It may also be useful to recognize the difference between the rules involving check, versus a rule that says that a player whose king is captured loses: a player who has any move available that does not put the king in *immediate* danger must play such a move, but if all of a player's moves would place the king in immediate danger when it isn't already, the game ends without the player being obliged to put the king in danger.  
  
  ---
  
  ### Answer by username_1 on 2015-01-07. Score: 2
  
  No. Check is check, even if the checking piece cannot legally move. There is extensive discussion of this in the answers to the question [illegal (?) move can put a king in check?](https://chess.stackexchange.com/questions/2348/illegal-move-can-put-a-king-in-check?rq=1).
  
  > **Comments:**
  > **username_0**: But can the player who moved his king into check make an illegal move?  
  > **username_1**: I don't understand your question. Can you update the original question with an explicit example?  
  
  ---
  
  ### Answer by username_4 on 2018-08-30. Score: 1
  
  I'd rather be more cautious and answer this question taking into account the time control used in the game because, as you will see, there are some concessions that regulations grant when the players have less time to think.
  
  ## If each player’s thinking time is at least 60 minutes:
  
  The move in question is indeed illegal, as others have commented. End of story. Even though nobody notices the irregularity for a while, as the rules indicate (emphasis mine):
  
  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.
  
  *End of story*?
  
  There might be a rare exception in case the game has ended (by checkmate or resignation) without the mutual check (or any other irregularity) being noticed, and the players have signed their scoresheets. I am not sure what happens if the illegal move is noticed after that because:
  
  5.1.1 The game is won by the player who has checkmated his opponent’s king. This immediately ends the game, provided that the move producing the checkmate position was in accordance with Article 3 and Articles 4.2 – 4.7.
  
  5.1.2 The game is won by the player whose opponent declares he resigns. This immediately ends the game.
  
  ## Rapid chess
  
  When all the moves must be completed in a fixed time of more than 10 minutes but less than 60 minutes for each player; or the time allotted plus 60 times any increment is of more than 10 minutes but less than 60 minutes for each player.
  
  In my opinion, the problem is more clearly described in other questions (both marked as a duplicate of this one):
  
  [Is it legal for a move to put both sides in check?](https://chess.stackexchange.com/questions/22395/is-it-legal-for-a-move-to-put-both-sides-in-check)
  
  [Simultaneous check](https://chess.stackexchange.com/questions/21493/simultaneous-check)
  
  Surprisingly, **the rules specifically mention the situation of a mutual check:**
  
  A.4.4 **If the arbiter observes both kings are in check**, or a pawn on the rank furthest from its starting position, **he shall wait until the next move is completed.** Then, if an illegal position is still on the board, he shall declare the game drawn.
  
  Otherwise, it is understood that the game can continue. For reference: A position is illegal when it cannot have been reached by any series of legal moves. (article 3.10.3)
  
  Now, if this actually happens in a real game, the use of the word illegal to describe the move after the game has ended is arguable, because the move was illegal at its time, but now it is part of a legal game supported by the rules!
  
  For other irregularities, the procedure is similar:
  
  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.**
  
  To be completely precise, these Rapid rules do not apply if certain conditions are met. According to A.3.1, the Competition Rules shall apply to Rapid chess (i.e. the illegal move cannot stand) if:
  
  A.3.1.1 one arbiter supervises at most three games and
  
  A.3.1.2 each game is recorded by the arbiter or his assistant and, if possible, by electronic means.
  
  Otherwise, the Rapid chess rules do apply and the illegal move has a chance to stand.
  
  Finally, I have to mention that these Rapid chess rules **also apply to Blitz**, when all the moves must be completed in a fixed time of 10 minutes or less for each player (or the allotted time plus 60 times any increment is 10 minutes or less).
  
  > **Comments:**
  > **username_5**: I think this answer misses the point: in all cases it **is** illegal to put one's king in check, and that's clearly what the OP was asking about. What happens *after* an illegal move is played indeed depends on the time control, but that's a bit off-topic here and might cause even more confusion for the OP.  
  > **username_4**: I thought it should be relevant because the rules specifically mention the OP's question. And the OP should know that if their opponent makes an illegal move in blitz **and** the OP does not notice the irregularity, it may stand.  
  
  ---
  
  