A few observations both Theoretical and Realistic:
1) 'T' - The eel-skin is not "attached to a hook to attract fish". It is part of the make-up of the overall fly. If "attract fish" is going to be the criteria, then any fly, or lure for that matter, would be prohibited.
2) 'T' - As stated by others, if a piece of skin is not permitted, then zonkers, mice with tails and similar flies would be prohibited.
3) 'R' - Is anyone really going to inspect a fly for its components?
4) 'R' - Other then the fly tyer, who will know that the fly has an 'illegal' component.
Many states need to improve the knowledge of the people writing many of these regulations and the daffynitions they use.