I don't know jow you could make a ban work. While I am totally against them, for a lot of reasons, the fact is it does bring sales to the store, they may not otherwise get. If i were to boycott store that sell dyed and tattooed fish, I would have nowhere to purchase products. I belong to an aquarium society, so most of my purchases are made at club auctions, and my boycott would have little effect on local LFS business.
I would suggest that a ban on store would not be practical, although, a ban on the sale of such fish, could possibly be legislated, although that would not be easy. If you could get the LFS to post that sign, that would be a major accomplishment. Removal of demand would definitely be the best solution. Consequently, I wasn't able to answer the poll as worded. Good luck with your efforts.