World Sailing Official Case Book
Case 106
When the string representing a boat’s track lies on the required sides of finishing marks or gate marks, it is not relevant that, when drawn taut, it also passes one of those marks on the non-required side.
Facts
As boats approach a downwind finishing line, a tidal current takes one of them outside one of the finishing marks. She sails beyond the entire finishing line, rounds the other finishing mark, and then crosses the finishing line from its course side.
Question
Has the boat complied with rule 28.1?
Answer
Yes. When the course requires boats to pass between two marks at a finishing line or at a gate, a boat complies with rule 28.1 if the string representing her track when drawn taut passes between the marks from the direction of the previous mark (see the definition Sail the Course). She complies with rule 28.1 even if the string also passes one mark of the finishing line or gate on the non-required side. In this case the boat passed the buoy serving as a mark of the finishing line on the non-required side before passing it on the required side.
See Case 90 for a discussion of a similar incident at a starting line.