In Pennsylvania, the only legal way to buy unpasteurized cider is from the the actual location where it is pressed. If its in a store, its been pasteurized some way. Sometimes heat pasteurization is used, but usually they run it through a UV light exposure machine that kills bacteria and yeast.
But just because its pasteurized, doesn't mean it has preservatives in it.
The pasteurization kills off e-coli bacteria as well as most of the wild yeast.
If you are getting it from a store, the label will have the ingredients.
If a preservative like potasium sorbate has been added, your yeast won't grow.
I think the flavor of the cider is better when you use the unpasteurized, unfiltered cider that you get directly from the orchard.
Having said that, I have made decent cider using commercial apple juice like "simply apple" that is available in the cold case at the supermarket.
All of the local orchards near me have discontinued making their own
cider because of the government regulations and the fear of being sued.