Dummy draws attention to an irregularity
Law 43A1(b): "Dummy may not call attention to an irregularity during play".
What if they do? OK you could fine dummy, but what about any damage or rectification? Suppose dummy points out that the wrong defender has just led? Is declarer now banned from noticing this?
Comments
Law 43 B distinguishes between the consequences of dummy doing something prohibited by Law 43A1 and Law 43A2, the latter being more serious.
If dummy had done something prohibited by Law 43A2, then Law 43B3 applies: the declaring side get no rectification for the defenders' irregularity, but the TD takes away any advantage to the defending side.
The implication is that there is no such restriction on rectification when dummy breaches Law 43A1 (which includes being the first to draw attention to an irregularity by the defence).
So you fine dummy if you think it appropriate (a warning would suffice except for a serial offender, IMO), but rectification for the defender's irregularity is assessed as normal.
If dummy draws attention, the TD must rule (Law 81C3). But dummy is subject to a warning or penalty adjustment.
Assuming the defenders are the offending side, the TD can use some discretion in ruling - not designating an exposed card as a penalty card, for example.
Where does that discretion come from (other than a feeling of fairness)? Under Law 12 Director's Discretionary Powers, his only discretionary action is to award an adjusted score.
Law 50:
A card prematurely exposed (but not led, see Law 57) by a
defender is a penalty card unless the Director designates
otherwise (see Law 49 and Law 72C may apply).
White Book:
8.50.4 Law 50, preamble: ‘unless the Director designates otherwise’
There is no limit in the laws on the ability of the TD to designate otherwise and it can be applied
whenever the other side has contributed to the situation that has led to the card becoming a
penalty card.
But in this case the card has been led, so Director cannot designate otherwise.
My answer was in response to your question about penalty cards.
Your earlier question about leads out of turn should be answered by L43B1, where a procedural penalty is the only sanction available. However, since the other side is the offending side in terms of the lead, there is no reason why they should escape the usual rectification.