North and South are allowed to "bid their hands". The Director will then follow the Laws.
I believe the information at hand is:
- Systemically, 2NT shows strong balanced hand.
- System over 2NT is some form of Stayman and Transfers.
- North plays "5=5 minors, weak" with several of her partners, and forgot South isn't one of them.
- In North's system where 2NT is minors, 2NT-3♦; 3♥ has no systemic meaning.
Now, I assume that given the AI to E=W (they heard the explanation, and the correction before the Opening Lead (right? South corrected the MI?)), that South took 9 or 10 of the last 8 tricks. But assuming the heart suit is unavoidably blocked, maybe there's an issue here. Let's go through it anyway.
Given that:
South is in possession of Unauthorized Information, and Law 73C requires that he "must carefully avoid taking any advantage from that unauthorized information".
South must also Alert per his correct system, and if 3
♦ is a transfer and that is Alertable/Announceable, he must do so. This will provide North with UI; that's what happens in face-to-face play. Not relevant to the ruling, but see below.
Unless South can show evidence that 3NT is his correct response to a transfer (which I also agree is possible, but I also agree would definitely be ahead of "I'm just bidding my hand" on South's excuse list!), then it is clear that he did not "carefully avoid" using the UI, but used it to try to salvage the situation. L73C continues: "A penalty may be assessed against a player who violates C1", and I'm definitely assessing one. Depending on the experience and obnoxiousness of the player, it might be a gentle explanation of his requirements. It might be a 1/4 board. In addition, at least in the ACBL, it would be sent to the recorder in case South has a habit of "just bidding his hand", and in my clubs, would be mentioned to the other directors for the same reason.
The director will then use L16 to assign a score. 3
♥ is clearly a LA not suggested by the UI (in fact, it's the automatic call), so now, what's North going to do? Remember here, while there would be UI for North at the table, for the purposes of evaluation of the auction, there isn't. Now, I know that there are many who will say "3
♥ doesn't exist, so partner must not have 5-5; oh yeah right, we don't play that, he thought I transferred, what do I do now?" is automatic. In my experience, in many auctions, it's not - "Oh, partner likes it, and is 1=1=6=5 or 0=2=6=5 with all useful cards and the
♥A" is also an option. But frankly, having played this agreement, that wouldn't occur to me, partner never has a good hand. I'd say "partner forgot again". So, let's take it to some Precision players, tell 'em they're playing 2NT is 5=5m, and give them this hand and auction, and see what they tell us. If the vast majority say, or at least mention "are we sure partner didn't forget and has a flat 20?", then we go with "3
♥ wakes up North", and we'll assign a reasonable call (likely 3NT. South will pass that). Defence will be based on "You know North thought it was 5=5 minors when she bid 3
♦, and then knew the real system when she bid 3NT (because she told E-W either at the time or during the clarification period (L20F4)." Which again should have some, possibly large, fraction of "9 of the last 8 tricks", assuming the information passed by N-S in the "assigned play" is sufficiently different from the actual play).
We'll also ask South about why he didn't Alert/Announce 3
♦ as required (assuming it's required). If there's any hint of "didn't want to give UI to partner", well, we're back into penalty mode. If it's "I was so shocked by the explanation that I lost my mind", sure, but still explain South's obligations to him.
End of At-the-table.
What South is required by Law to do is to Alert/Announce the transfer, and bid 3
♥ (Cyberyeti's caveat excepted). Assuming he does this, North now has UI that could "wake her up" to the real agreement. Now *she* is bound by L73C. But the same polling above that said "partner must have 20 BAL, even if our system is 5=5m" applies here, and means the only LA is "3NT, and guess what to do when 4
♥ comes back to her." Luckily, 4
♥ doesn't come back to her, so she doesn't have to guess.
I know, I know, club game, minimal (and playing) TD. That's why South gets away with "bidding his hand" a lot, because he's never called on it, and the directors don't get to know that he does (and when the director at his table calls him on it, a different kind of hell breaks out). As a (slightly better than minimal club) TD, I have that problem in spades, even in games where I'm playing and not directing, and especially in clubs where I'm not a regular or a director. The answer is either "if they need to do that to win *this game*, let 'em. Not worth it." or "improve the directing in general at the club so that this gets noticed by more directors, and more players who get ruled against by more directors" or, especially if I can't let go for the former and the directors aren't interested in the latter, volunteer to do some of the directing myself. But there's a lot of the former, and just enough of the latter that I don't get labelled a Rules Lawyer who can't tell the difference between the Vanderbilt and a -ing club game *by the directors*, never mind the players.
When I go to sea, don't fear for me, Fear For The Storm -- Birdie and the Swansong (tSCoSI)