Interference covers more than contact: blanketing, taking wind, making waves at close range, or forcing a course change.
23.1
A boat that is not racing (finished, retired, waiting for her start, or a boat from another fleet) must not interfere with a boat that is racing, if reasonably possible. Unlike most of Part 2, a boat can be penalized for breaking this even when she is not racing.
23.2
A racing boat must not, if reasonably possible, interfere with a boat taking a penalty, a boat sailing on another leg, or a boat returning to start under rule 21.1. After the starting signal this does not apply when the interfering boat is sailing her proper course. It is the rule that stops a boat on the run deliberately blanketing a beating boat.
Common situations
Finished boats at the line
A boat that has just finished and is sailing back through the line to the committee boat is not racing. If she blankets or crosses close ahead of boats still finishing, she breaks rule 23.1.
Changed in 2025
There is no rule 24 in the 2025–2028 book. Older references to rule 24, Interfering with Another Boat, are to what is now rule 23.