Is the Shark Bite product illegal in Vermont?
The major reason for plumbing items to be forbidden (specifically in Vermont) is that they are not "Lead-Free" which Vermont has been an early-adopter state in requiring.

The following from Shark-Bite would appear to indicate that this should not be a problem with any fittings that have not been sitting around for 5 years or more:


  SharkBite Push-to-Connect Fittings
  
  The SharkBite push-to-connect range is made from Lead Free DZR Brass
  and all products were converted as of October 2012. The standard
  material versions of SharkBite push-to-connect fittings are no longer
  in production, but we do continue to offer a small range of 5/8″
  fittings in standard material, specifically intended for radiant
  heating applications. As a running change, these fittings will be
  converted to Lead Free in due course. Our SharkBite 2XL Large Diameter
  fittings have been Lead Free since their introduction in February
  2011. SharkBite PEX/barb fittings
  
  Our PEX/barb range is made from Lead Free DZR brass and all products
  were converted as of October 2012. We have also implemented an
  extended range of engineered polymer barb fittings.