Say I somehow make an illegal move of any kind. Can I then make it legal? If so, how? What are all the ways an illegal move can be legal?

closed as unclear what you're asking by Scounged, Herb Wolfe, GloriaVictis, Brian Towers, Dag Oskar Madsen Aug 21 '18 at 12:44

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  • 3
    Can you precise what you mean by "make an illegal move legal" ? An illegal move is by definition, illegal. But if d2-d4 is illegal at some point because you have a bishop in the way on d3, then removing this bishop would possibly make a later d2-d4 legal. Maybe you mean smg else altogether, but you need to explain yourself. – Evargalo Aug 20 '18 at 14:25
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    Yes, you need to explain. Another option to the one mentioned above: Under some rules, if you make an illegal move (e.g. leaving your own king under attack) and the opponent (or arbiter) points it out, you are forced to take back that move and make a legal move. Typically in such situations a time bonus is added to the opponent's clock. – user1583209 Aug 20 '18 at 14:53
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    If you make an illegal move, and you notice right away, you are usually allowed to change it into a legal move. However, you need to move the piece that you touched if possible. (There is more to be said about this, but I am not sure this is at all what you want.) – quid Aug 20 '18 at 15:35
  • -quid , yeah that's what i wanted – RuhanUR Aug 21 '18 at 14:20
  • What do you mean by "By anyway?"? – Peter Mortensen Dec 30 '18 at 16:19

It is possible for a position to change in such a way that an illegal move becomes legal. As one example, if a move would result in your king being in check, then it is illegal, but if you make one (or more) move(s) so that later the same move would not result in check, then it becomes legal. The following diagram presents one such situation:

[FEN "q1k5/8/8/8/8/8/1Q6/1K6 w - - 0 1"]
[StartFlipped "0"]

1.Qa2 Kb7 2.Ka1

In the beginning position of the above construction, the white king cannot move to a1, since that would be check. However, if white first moved their queen onto a2, then they would be able to move their king to a1 later.


In blitz I believe if you make an illegal move and your opponent doesn't notice it, and then completes their move, the position stands as valid.

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