In the old Orange Book, there was a regulation that "a player who is not sure whether a call made is alertable, but who is going to act as though it is, should alert the call." This implied that if the player was going to take the bid as natural, he should not alert. This contradicted another regulation that "If a player knows partner’s call is (or may be) alertable, but cannot remember its meaning, he should alert."
If players had no specific agreement in a situation, but they were following (different) general principles, one would think a bid was natural, while the other thought it was conventional. However, the bid would only be alerted half the time (when the bidder thought it was natural), and the rest of the time, the opponents would have no reason to suppose anything untoward was happening.
The auction that brought this to a head was:
The 2 bidder had intended his bid as forcing (an inverted raise), but the pair had no agreement in this situation (note that this is different to having an agreement not to play something). The overcaller reopened, the opposition bid game, and he claimed damage. He got a partial adjustment (if he’d known the opposition had no agreement, he’d have passed some of the time), but the L&E was concerned that under the OB wording, the opening side had not committed any infraction.
We therefore decided that "no agreement" situations should be alertable. We didn’t want to phrase it like that, as then pick-up partnerships would be required to alert everything. What we wanted to do was cover the situation where a regular partnership has general rules, but the partners are applying them differently. The opposition are entitled to know that there is no understanding about a bid (as opposed to it being natural), and an alert is the means to do this. If asked, the player should say "no agreement", explaining the possible meanings.
The two relevant paragraphs in the Blue Book are:
2 D 2: Unless a player knows that his partner’s call is not alertable (or announceable) he must alert. If the player is unsure when asked for its meaning he may refer the opponents to the system card if it is likely to be on the card. If there is no relevant partnership understanding, he must not say how he intends to interpret his partner’s call. See also 4A6
4 A 6: If there is no alert and no announcement, opponents can assume that the call does not fall within an alertable or announceable category, through either explicit or implicit understanding. See also 2D2
We have reviewed several appeals which suggest the TDs have not recognised this change. Example auctions were:
The 3 bidder thought that 3 was asking for a stop; partner thought it was showing spades.
The doubler thought it was penalties, partner thought it was takeout.
In both cases, there was no specific agreement, and the TDs ruled:
The L&E view is that in both cases, there should have been an alert.
Note that this alerting requirement only applies when there is no agreement. The more normal case, where there is an agreement but one player has forgotten, is still dealt with using the current UI and (depending on who forgets) MI regulations.
The "no agreement" alert is there to ensure that the opponents are made aware of the systemic agreements (or lack of them). An unalerted bid can then be assumed to be natural (unalertable).