Here is the logical fallacy in banning ivory (and mammoth fossil):
A = B = C, therefore, A = C
A (ban ivory) = B (reduce demand) = C (reduce poaching)
"State bans like the one Hawaii signed into law late last week are critically important to reducing U.S. demand for ivory, and, as a result, poaching in Africa."
All it will do is decrease the supply, not necessarily the demand. As with other attempts to control appetites & desires through legislation (i.e., prohibition, drug war, gun control, etc.), the ban will NOT reduce demand, it will only turn otherwise law-abiding citizens into criminals and quite possibly even increase poaching as the price of ivory will skyrocket (law of supply & demand) and thus, make ivory an even more lucrative commodity and attractive to poachers to obtain and sell on the black market.
While I agree with the intent of the ban (to protect elephants from illegal poaching), I feel the methodology is flawed.