This situation was given to me.
2 : 2
2N : 3
5 : 5NT
2 showed some values but not 3 controls
2N is a balanced 22-23
3 is a transfer to hearts (not alerted)
5 was bid after a long pause
5NT (-1) was the final contract - after review the TD ruled the score back to 5 -2.
Obviously the player must carefully avoid taking advantage of the UI (73C) but we do need to look at law 40a
- Information conveyed to partner through such understandings must arise from the calls, plays and conditions of the current deal. Each player is **entitled to take into account the legal auction **and, subject to any exclusions in these laws, the cards he has seen. He is entitled to use information specified elsewhere in these laws to be authorized. (See Law 73C.)
Since 5 is an impossible bid in their system ( 4 would show a good fit, slam interest and a cue in diamonds), I would argue that 5NT should be allowed since there are no logical alternatives.
Why do I say that?
Because law 16B says
(b) A logical alternative is an action that a significant proportion of the class of players in
question, using the methods of the partnership, would seriously consider, and some
At the point where the 5NT call is being considered (as well as pasing 5 or bidding 5 or even 6) the partnership has no methods - thus no logical alternatives.
Or does 73C by itself force a pass (or a raise to 6 ) notwithstanding 40a.