At the moment the two rules compromise each other. And it doesn't help that the the later rule says "should".
BOF Rules, 1.3.4 - Ignorance of these Rules, or of any other instructions issued by the Organiser whether with pre-race information, prominently displayed at the event or by any other reasonable means, shall not be accepted as a satisfactory explanation for any infringement.
Appendix B, 3.1.21 - Uncrossable boundaries (ones which it is forbidden to cross) which affect the course should be indicated by overprinting the mapped feature with a solid line