well, I know nothing about Maine law, but a quick check of their statutes reveals this:
Title 29-A, Chapter 15, Section 175
4. Fenders. Except as provided by section 1953, subsection 2, paragraph E, a motor vehicle other than a street rod must be equipped with fenders or fenders and extensions. When a wheel and tire are installed that permit the tire tread to extend beyond the natural fender configuration, the fenders must be modified or extended to cover the exposed tire tread. [1993, c. 683, Pt. A, §2 (new); Pt. B, §5 (aff).]
I didn't see any other statutes dealing with the topic in my quick look, and I didn't look at the administrative regs at all. But this seems to indicate that while you have to have the tread covered, the material used to do so is left to your discretion. You can look for yourself by going to the state's website and following links. I'd suggest you look through the related regs yourself. Good way to learn all kinds of stuff you never knew!
