Product Unavailable to a certain zone

Can I do this? I have a product that I want to make unavailable to a certain state. I can see the zone is set up but I cannot figure out how to stop the product from being paid for or downloaded by people with that address.
All products are downloadable if that makes a difference.

First, you need to decide if guests can add these products (or any products) to the shopping cart or ... do they login first to know the address ...

Next, are the products unavailable to addresses based on payment address or shipping address?

Then there needs to be a test made based on these decisions on the products ...

Consider if on shipping address then you might want these products to be added to the cart and flagged about the shipping address requirement and then prevent the customer from getting past the checkout_shipping until the address is right ...