USCF: Should the arbiter correct illegal moves without a player claim?

Question

Should an USCF arbiter correct illegal moves without a player claim?

Here is the USCF link: USCF rules of chess

Here is the FIDE link: FIDE rules of chess

USCF and FIDE rules are NOT 100% equal.

What does FIDE require from their arbiters?

Please cite the rule.

My perspective is the following:

• According to USCF rules, if players are in time pressure,
  the arbiter cannot correct illegal moves without a player claim. Time pressure in USCF is defined as "a situation where either player has
  less than five minutes left in a time control and the time control
  does not include an increment or delay of 30 seconds or more."

• According to USCF rules, if players are NOT in time pressure, the arbiter can or cannot correct illegal moves without a player claim, but the
  arbiter needs to use the same criteria in all the tournament games.
  The arbiter does not need to announce in advance which preference
  he/she will use. I would prefer, but it is not mandatory, to not
  correct illegal moves without a player claim in any circumstance
  because just one criteria would be used.

It seems that these are the FIDE rules related to this question:

Answer 1

Yes, you're correct about USCF rules. Rule 11D1 says the director may not correct illegal moves in time pressure. Outside of time pressure the director has the option of using 11H and correcting illegal moves or 11H1 and not correcting them, but cannot switch between the two.

I would also point to rule 21D which lists the ways the director may intervene in a game:

21D. Intervening in games.
The director’s intervention in a chess game shall generally be limited to the following:
...
21D2. Correcting illegal moves observed.
Correcting any illegal moves observed, unless time pressure exists (11D1) or Variation 11H1 is used (the director does not correct illegal moves unless asked by a player).

As you can see, 21D2 lists correcting illegal moves as one of the limited ways the director may intervene in a game (unless an exception applies).

As far as FIDE rules go, I see nothing prohibiting an arbiter from correcting an illegal move. Rule 7.5.1 says in part:

If during a game it is found that an illegal move has been completed, the position immediately before the irregularity shall be reinstated.

Rule 12.1 says

The arbiter shall see that the Laws of Chess are observed

which may indicate a duty to do so, but I'm less confident in that. Rule A.4.2 explicitly says the arbiter should intervene if they see an illegal move, but that rule only applies in rapid games. This might indicate that there isn't a duty to do so outside rapid games (why would they spell out that duty here, but not in the main rules, if it applies to both?)

Answer 2

Should an USCF arbiter correct illegal moves without a player claim?
What does FIDE require from their arbiters?

Under the FIDE Laws arbiters do not correct illegal moves (except in one special case) but they do flag them, require the player to correct them and punish the player.

In standard time control chess:

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.

This basically says that if the arbiter knows an illegal move has been made, whether spotted by the arbiter, flagged by one of the players or even by a spectator to the arbiter, then the arbiter must act, require the move to be corrected to a legal one and punish the player.

The definition of "illegal move" is also very broad. It includes pieces moving in a way other than specified by the rules, moves that fail to get the king out of check or put the king into check, but also includes these:

7.5.2 If the player has moved a pawn to the furthest distant rank, pressed the clock, but not replaced the pawn with a new piece, the move is illegal. The pawn shall be replaced by a queen of the same colour as the pawn.

Only in this case does the arbiter correct the move played

and

7.5.3 If the player presses the clock without making a move, it shall be considered and penalized as if an illegal move.

and

7.5.4 If a player uses two hands to make a single move (for example in case of castling, capturing or promotion) and pressed the clock, it shall be considered and penalized as if an illegal move.

For blitz and rapid the rules are different, partly because the moves are not recorded and partly because a sequence of moves can be made very quickly making intervention difficult.

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.

So, the arbiter may only intervene if no more moves have been played. If no more moves have been played then the arbiter should intervene but is not at fault if they are too slow or miss the move.

Of course where illegal moves are made and not corrected this leaves the possibility of illegal positions arising which are difficult or impossible to correct. Hence the next rule for rapid and blitz:

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.