There is no need for a law to get people to adopt shelter animals. Just have ads for them on TV and the newspapers... people will adopt them.
When I lived in CA, I did not need to adopt animals ever. Cats just showed up in my yard.
After three of my yard cats died over Easter week, I did go to an animal shelter to get a new cat. Apparently, in my new neighborhood, there are no stray cats looking for a home.
To make a law to require pet stores to sell shelter pets is ludicrous. Most pet stores do that voluntarily. I checked all of the local pet stores and the shelter to find the perfect cat.
I suspect foul play.
Yard cats are the only cats worth having. They are eternally grateful.