Law 45 C Card deemed to be played
Law 45 C 4 b allows declarer to correct an unintended designation of card from dummy after a slip of the tongue but not after a loss of concentration or reconsideration of action.
The Commentary on the laws clarifies that the option to change a designated card in dummy is restricted to cases where declarer has named the card. If he has played the card from dummy by touching it or placing it in a played position on the table the card cannot be changed.
The action by declarer of playing a card from dummy by pointing at it is not covered.
If declarer, for instance, points at the lowest card of a suit in dummy and then raises his finger to point at the highest card, or vice versa, how should we rule? The action could be interpreted either as a reconsideration of action or a movement of the finger starting low and going up (or up and then down). The declarer will naturally say it was the latter.
This situation actually happened yesterday.
Comments
I don't think this counts as a designation. The laws you quote defintely don't cover 'pointing' - see below.
B. Play of Card from Dummy
Declarer plays a card from dummy by naming the card, after which dummy picks up the card
and faces it on the table. In playing from dummy’s hand declarer may, if necessary, pick up
the desired card himself.
C3
purpose either of arranging dummy’s cards, or of reaching a card above or below the card or
cards touched.
So I think that we rule that no card has been played. (It is similar in some respects to declarer detaching a card from his hand and then replacing it. Provided the criteria in 45C2 aren't met then the card isn't played.)
(I suppose 74A2 might be considered, but that is a long shot.)
I think the use of the word "designation" indicates a broader application than just spoken instruction and I would expect it to include pointing at a card. That said, I find it hard to see how a card could be inadvertently (to use the old terminology) pointed at.