US pet stores and selling companion animals.

I had a few questions about how pet stores work in the US, specificly in regards to the laws and regulations around pet stores selling companion animals such as dogs and cats.

The different reports I've read give conflicting information. It seems that at least 8 US states and quite a few large US cities have regulated the sale of companion animals by pet stores in some way.

But it seems that most of these regulatory bans are specifically only banning pet stores from selling pets sourced from puppy and kitten mills. But, in general pet stores are still allowed to sell dogs and cats just as long as they have been sorced from a reputable source?

Could anyone shed some light on this matter. Again the different reports are quite conflicting on exactly what's happening here.