It is not unconstitutional at all. The following case illustrates the WA courts finding any person of reasonable intelligence should be able to find seatbelt manufacture standards by a simple search of the internet. The case noted was for "federal standard 208". In your case the issue is "federal standard 209". I suggest you pay the ticket and not make a fool of yourself in court.

http://biotech.law.lsu.edu/cases/pp/ECKBLAD.htm

http://www.law.cornell.edu/cfr/text/49/571.209











http://www.law.cornell.edu/cfr/text/49/571.209