RMB1, on 2014-June-13, 06:33, said:
If a pair has a way of showing a singleton after a 1NT opening:
is the call that shows the singleton an illegal agreement?
is a 1NT opening an illegal agreement if they subsequently show a singleton?
is a 1NT opening an illegal agreement even if they don't show a show a singleton on this auction?
This explanation is only valid in ACBL jurisdictions.
Pursuant to ACBL authority (whether you want to call the authority regulation, opinion of those in power, historical practice or whatever), the following appears to be correct:
The agreement that the partnership has to determine if a natural opening 1NT hand has a shortness (singleton or void) is not an illegal agreement.
However, the fact that the partnership has this agreement implies that they also have an agreement that the natural 1NT opening bid may contain a shortness. It is the agreement about the natural 1NT opening bid that is illegal. One is permitted to open a natural 1NT with a shortness as a deviation from standard practice (hence the use of the term "generally" in the description of the distributional requirements concerning a natural 1NT opening bid). One may not have a partnership agreement that a natural 1NT opening bid may contain a shortness.
The fact that a natural 1NT opening bid on any particular hand does not contain a shortness doesn't change the fact that if a partnership has an agreement to determine if the natural 1NT opening bid contains a shortness then the partnership has an implied agreement that the natural 1NT opening bid may contain a shortness. The agreement concerning the distributional requirements of the natural 1NT opening bid is still an illegal agreement.
I have been very careful in this explanation to use the phrase "natural 1NT opening bid" or some variation on that phrase. None of this discussion applies to any conventional 1NT opening bid, such as the Dynamic 1NT opening bid of the Romex system.
EDIT: The foregoing is my understanding of the way things ARE. For a very well framed argument about the way things should be, see David Yates' post timestamped about 11:00pm EST Thursday, June 12, on this bridgewinners thread:
http://bridgewinners...ingleton/#new_1