Have a look at:ISAF Q&A 2009-026
I've been stewing on this one for a couple of days and am still not happy.
Couple of additional questions:
What if boat X just skips one mark? Or rounds it the wrong way? Is she then not on the next leg of the course? She cannot - according to this Q&A - be finishing when crossing the line. She's never on the next leg, let alone on the finishing leg. She can and may correct her mistake any time, if the SI don't specify a time limit, the next day for that matter....
This one will be impossible for the RC to comply with. The people on the finish boat don't have the time nor the position to check if every boat that crosses the line, has complied with RRS 28.1. There are perhaps enough mark-boats at an International big event to check every rounding, but not at my local events. We just don't have the "manpower" or the boats. Do you?
So the people on the committee finish-boat will sound the horn and record a boat as finished. Only after protest, will the boat be DSQ-ed for not sailing the course.
Next, if the boat is not on the next leg of the course, what about rule 23.2? In a fleet race you cannot help but interfere with several boats who are then apparently on another leg. So you better be on a proper course ALL the time.
Also, rule 18 would be "off" for each subsequent mark rounding. Boats are not on the same leg of the course and one of the boats does not have a required side to which she must leave the mark....
Second half of this Q&A: What about the requirement in RRS 61.2; Informing the other party at the first reasonable opportunity?
If you don't want make your opponent aware that he has made a mistake - tactically sound - you should keep your mouth shut. If you protested later, the PC might ask "Was this the first opportunity, after you became aware of the error, that you could have informed the other boat?"
Out goes the protest with validity….
Or do you want to go with the premise that a boat hasn't broken RRS 28.1 until it's to late to correct that? Then you will have to wait until end of finishing time, find the boat or representative in the boat park and inform them of your protest.
We will have to comply with this interpretation of the rules, but in practice it will be very very difficult.