An illegal move in chess doesn't just mean taking it back — in tournament play it awards your opponent extra time, and a second offense costs you the game. We break down every line of FIDE Article 7 with examples.
⚠️ Official Rule: FIDE Article 7.5
First illegal move: Opponent receives 2 extra minutes.
Second illegal move by same player: That player loses the game (draw if opponent cannot possibly checkmate).
1. What Is an Illegal Move?
Under FIDE Article 7.5.1, an illegal move is considered completed when the player presses the clock. At that point:
- The arbiter restores the position immediately before the violation.
- If that position cannot be determined, play resumes from the last identifiable position.
- The opponent receives 2 extra minutes.
2. Leaving the King in Check (Article 3.9.2)
No piece may be moved so as to expose the player's own king to check or leave it in check. This applies to two common situations: moving a pinned piece, and moving the king to an attacked square.
3. Illegal Castling Attempts (Article 3.8.2)
Castling rights are permanently lost if the king or the relevant rook has previously moved. Castling is temporarily prohibited if the king is in check, passes through an attacked square, or lands on an attacked square, or if any piece stands between king and rook.
4. Pressing the Clock Without Moving (Article 7.5.3)
Pressing the clock before completing a move is treated as an illegal move. This includes rok and promotion situations where the sequence is not fully completed.
5. En Passant Errors (Article 3.7.3)
En passant is only valid if your pawn is on the 5th rank, the opponent's pawn advanced two squares on the immediately preceding move, and it is on an adjacent file. The right expires immediately if not used on that very move.
6. Promotion Errors (Article 7.5.2)
A pawn reaching the back rank must be replaced by a queen, rook, bishop, or knight of the same color. Pressing the clock before placing the new piece is an illegal move — the pawn is automatically replaced by a queen.
Conclusion
Understanding FIDE Article 7 gives you a tangible edge at the tournament board. Knowing your rights — and your opponent's obligations — can convert an illegal-move violation into a decisive time advantage.
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