This hand arose in the penultimate round of a four-session, eight-round Swiss pairs event involving the then leading two pairs.  EW were playing 2/1 with a short club opening with transfer responses, a 14-16 1NT and a light opening style. 

The jurisdiction is Australia with the relevant extract from the ABF Alerting Regulations:

3.3 Alerts during the Auction

3.3.1 If a call is conventional, it must be alerted (unless it requires an announcement or is self-alerting).

3.3.2 Two classes of natural calls must be alerted (unless they are self-alerting), viz.

(a) The call is natural, but there is an agreement by which the call is forcing or non-forcing in a way that the opponents are unlikely to expect. Examples:

• Responder’s first round jump shift on weak hands.
• A non-forcing suit response by an unpassed hand to an opening suit bid (whether or not after intervention).
• A pass which forces partner to take action (e.g. SWINE).

(b) The call is natural, but its meaning is affected by other agreements, which the opponents are unlikely to expect. Examples:

• A natural NT overcall (or response) in the direct position, which does not promise a stopper in the overcalled suit.
• A jump raise of opener’s one-level bid in an uncontested auction, which may be weak or preemptive.
• A single raise of partner’s suit which may be strong or forcing e.g. 1♦ - 2♦ forcing.
• The rebid in a canapé sequence where the second suit may be longer than the first.
• A 1♥ opening, which denies holding 4+♠.

Prior to his final pass, North inquired as to the meaning of all bids in the auction at which point it was revealed that West was 15-16 and unbalanced with ♦ support.  South called the Director to draw attention to the apparent irregularity of the failure to alert both 1NT and 3♦, but was careful to not suggest what remedy he was seeking (although it was fairly obvious that changing his double to a pass was what he was looking for).

The Director ruled that neither 1NT nor 3♦ were alertable, would not allow South to retract his double and instructed that the auction and play continue.  North and East passed, North led ♠A and continued with ♠T which declarer successfully won in dummy with the Q and came to 12 tricks after South pitched a ♥.

The Director was called back to the table with South contending that absent any alerts of West's bids, it was reasonable for him to presume that West was around 11-13 and with East being a passed with a light opening style, he was essentially doubling the auction which he would not have done had he been aware that West could be 15-16 unbalanced.

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