19G. Sealed move invalid.
If the envelope contains no sealed move or the sealed move is illegal and the director finds there is no reasonable
interpretation of it, the player who sealed the move loses the game.
Question 1: How can a director reasonably interpret an illegal move? If it is illegal, what is there to interpret?
Question 2: Am I as a TD required to call the game lost to the illegal mover where I don’t find a reasonable interpretation, or do I have leeway to not call the game a loss? Is this a must situation where I must give a win to the opponent?
Writing Rb2 instead of Rb7 when the only rook is on e7 allows a reasonable interpretation that Rb7 was intended (a common mistake is to reverse the numbers, particularly when the board is either unnumbered or is set up with White on the 7th and 8th ranks). Writing h4 when the only pawn is on the a file can be reasonably interpreted as a4 (reversing the letters is another common mistake). KxB when the only enemy piece next to the king is a rook can be interpreted as KxR (accidental closure of the bottom of the R). White writing h7=Q when the pawn is already on h7 can be interpreted as h8=Q.
Note that I used the word “can” rather than “should”. A TD may not find such interpretations to be reasonable and may opt for a simple illegal move loss (re-read rule 1A). The spirit of rule 21F3b might inspire some TDs to be more willing to accept a reasonable interpretation that allows the game to continue.
PS asking the sealing player what the move was before opening the envelope can make the decision on reasonability easier. If they move the knight from d5 to b3 instead of b6 then the otherwise reasonable Nb6 interpretation can be rejected.
When sealed moves were a common thing - folks who sealed would most likely take extra caution to write their move accurately and clearly – but not always. Sometimes when the TD would give instructions to seal a move they would remind the sealing person.
So if you sealed what looked more like an e5 instead of d5 and there are no other pawns left and take it a step further that no other piece could move to e5 - you could interpret the written e5 was d5. Of course, this is an easy one and in other cases there are just too many possibilities to interpret what was meant and you have to judge it as a loss. Use your power wisely.
I had this rule applied incorrectly by a NTD/NM once. My opponent sealed an illegal move, not knowing the exact rule I claimed that illegal move is automatic loss and the TD agreed. However, it was pretty clear what he meant with any other interpretation being a much bigger stretch!
A sealed move should be unambiguous and legal. If there’s any doubt about it, then I would declare it an illegal sealed move.
But as others have noted, adjournments are so rare these days that many TDs probably don’t even keep sealed move envelopes on hand.
The player sealing the move needs to check that the move they wrote down is not subject to interpretation. Not all TDs (or arbiters) are strong chess players.
I think the sealed move envelopes that US Chess sold cautioned the player to make sure their move was unambiguous and legal.