Yes he is if he believes a rule has been broken. Top of Page 11 in the Blue Book (my emphasis)
SPORTSMANSHIP AND THE RULES
Competitors in the sport of sailing are governed by a body of rules that they are expected to follow and enforce. A fundamental principle of sportsmanship is that when competitors break a rule they will promptly take a penalty, which may be to retire.
The copy on board WOXI must have been eaten by moths.
Yep get that but am not 100% on enforce means must protest though for sure I understand you pointing out the inference.
Am wondering how that impacts on a third party who witnesses a non contact infringement.
I'll go do some reading.