You are East. Declarer (South) plays in NT having denied 4 spades in the auction. Partner leads ♠2 (leading style: 4th highest leads from length to an honour, 2nd highest without an honour). Declarer wins trick 1 with ♠10, cashes ♠A (all follow), plays ♠4 to the 9 and Q so you discard. Now at trick 4 declarer plays ♠K, discard from you, discard from declarer and partner starts thinking.
You know from the bidding and play in the spade suit that partner has the remaining spade (the jack) but you also know (from UI) that she appears to be thinking about what to discard, apparently having forgotten that she has a spade left.
Can you say anything to stop partner revoking?
At the table, I did nothing as I am familiar with the wording of Laws 73A1 and 73B1 regarding communication with partner.
Subsequently it occurred to me that a different Law could be relevant:
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Does this Law permit me to remind partner of her requirement to follow suit? If it does, how can I do so without breaching Law 73? Or should I adopt the WBLFC approach of pretending that Law 73 does not exist when it suits me?
Alternatively, is it acceptable for me to ask declarer "Have you no more spades?" (Law 61B3) in the belief that declarer is unlikely to have revoked but secretly hoping that partner will overhear and be woken up? Or is that an improper question solely for partner's benefit (Law 20G1)? [Yes I know that Law 20 is titled "REVIEW AND EXPLANATION OF CALLS"] but we are told in the Introduction to the Laws that "Where headings remain they do not limit the application of any law".]
Which Laws take priority and why?