[Nancy1999]

According to the AKC rules of conformation/showing:

RULES DISMISSALS
[R] Lameness, Excusal: It is the judge’s sole
responsibility to determine lameness. It is not subject
to protest. The judge shall excuse a lame dog
from the ring, withhold awards from that dog and
mark the judge’s book “excused, lame.” (Rules,
Chapter 11, Section 8b).
[R] Change in Appearance, Disqualification A dog
which has been changed in appearance by artificial
means, except as specified in the standard for its
breed, may not compete at any show and is to be disqualified
(Rules, Chapter 11, Section 8).
A dog is considered changed in appearance by artificial
means if it has been subjected to any type of procedure
that has the effect of obscuring, disguising or
eliminating any congenital or hereditary abnormality
or any undesirable characteristic, or anything that
improves a dog’s natural appearance, temperament,
bite or gait.In addition, the insertion of any type of apparatus in
the mouth of a dog disqualifies that dog from competition
in dog shows and subjects anyone who exhibits,
or causes to be exhibited, such dog to disciplinary
action. http://www.akc.org/pdfs/rulebooks/REJ999.pdf