NC law enforcement is going to have to do better roadside testing than just looking at labels if they want to prove a helmet as non-compliant.

Some helmets bought new did not have DOT labels on them, yet the NHTSA does not say there is any compliance issue. There are also people who put a sticker or tape or paint over their labels, or remove their labels, and this is not a violation of federal law if it is their own personal helmet. The lack of a visible DOT sticker does not necessarily mean they do not comply. 

NHTSA Interpretation Files -
this particular file will be handy for NC bikers who remove or cover the DOT label.

Correspondence from Erika Z. Jones Chief Counsel, NHTSA
http://isearch.nhtsa.gov/files/3315o.html

"Please note that Federal law does not prohibit the helmet's owner or any other person that is not a manufacturer, distributor, dealer, or repair business from removing the label from motorcycle helmets. Thus, the owner of a motorcycle helmet is permitted to remove the label from his or her helmet for any reason without violating any provision of Federal law."

Also, note that some helmets prior to Oct 1988 did not fit in a Size C headform thus FMVSS 218 did not apply to them, so there was not a non-compliance issue. If your helmet was made before October , 1988, helemts without a DOT label are not necessarily non-compliant. Can the prosecution prove that your helmet was made after October, 1988?

For other interpretation files, go to http://isearch.nhtsa.gov/Index.cfm put helmet in the search box and click on search now. We are sure to find many useful paragraphs.