Brett Horton writes, while quoting a UCI member:
"He stated that while the use of the rainbow stripes in the middle/body of the jersey is limited to use only by the current world champion, and only for use only in the discipline to which the jersey was won, collars and neck bands fell out of the scope of their scrutiny. Hence you have situations like the one Ray Green put forth of a pro road rider wearing CdM bands on his jersey to commemorate his junior track world championship."
UCI amended their rules this year. A rider can now only wear the piping of a former world champion on his jersey when racing in the discipline in which he holds the honor. Here is the UCI rule:
1.3.064 When he no longer holds the title of world champion, a rider may wear rainbow piping on the collar and cuffs of his jersey as per the technical specifications in the brochure which will be sent to him by the UCI. However, he may wear such a jersey only in events of the discipline and speciality in which he won the title and in no other event. (text modified on 1.01.05; 1.09.05).
Lou Deeter, Orlando FL. Helped with this by former listmember Jonathan Greene of Oviedo FL.