While racing, boats AW and BL are approaching an obstruction that can be passed on either side. Both boats are heading towards the middle of the obstruction. At position 1, AW is clear ahead by a very narrow margin and on a track to windward of BL. At position 2, they have become overlapped with AW to windward of BL.

Question 1
At position 1, AW is clear ahead and thus has right-of-way under rule 12. When the overlap between them begins, BL becomes the right-of-way boat under rule 11. Rule 19.2(a) states that the right-of-way boat may choose to pass the obstruction on either side. How can we determine which boat has the right to choose in this situation?

At any point in time, the right-of-way boat at that moment is entitled by rule 19.2(a) to choose on which side she will pass the obstruction. Therefore, while AW is clear ahead of BL, she has the right to choose to pass the obstruction on either side. When the boats become overlapped, AW loses that right, and at that time BL has the right to choose.

Question 2
What rules apply as the right-of-way boat exercises her right to choose on which side to pass the obstruction?

Answer 2
When a right-of-way boat acts to implement a choice she has made under rule 19.2(a), she must both give the other boat room to keep clear of her and also comply with any applicable rules of Section B.

Rule 19.2(b) applies if the boats are overlapped. If they are, the outside boat must give the inside boat room between her and the obstruction, unless she has been unable to do so from the time the overlap began.

Rule 43.1(b) applies while the inside boat is sailing within the room to which she is entitled under rule 19.2(b). However, it will not exonerate her if she is the right of way boat and she breaks rule 19.2(a).