There wouldn't be any suppliers if there wasn't any demand.

Ie you could introduce a licencing system and enforce it. Only licenced people could supply puppies and the licence would be revoked the minute the puppies or their parents were found to be living in unacceptable conditions that would need to be clearly defined and easy to measure and enforce. Puppies would be housed with their mum in large spaces and buyers would view via web cam. Buyers would need to pass a licence test to prove they know the basic needs of a puppy, training, and care and feeding. People who tick the box for feeding chocolate and rubbing puppies nose in it - would fail. Puppies would be microchipped before they could be sold. Ideally I'd want them vaccinated and wormed and flea treated too and maybe desexed if the buyer didn't pass the responsible undesexed dog owner test.

I reckon there wouldn't be nearly as much crime associated with drugs if clean drugs were available on prescription for those who wanted them. I am uncertain how you'd manage addictions but I'd much rather someone gets a clean hit over the counter for $20 than nick the tv out of my house or mug me for $50 for their dirty hit.

The worst drug in terms of damage to the community and personal health is alcohol and I must say I don't think we manage people addicted to legal drugs very well either.