Validate the shipping form?

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I'm a developer and I'm facing a problem... is it possible, in anyway, to validate the fields in the shipping address section of the checkout page? 

I would like to limit some products (frozen food for example) to be shipped to addresses that are within 20km from my physical store.

Every solution that I can think of, is a bad one because allows the user to lie about an early address check and then put a different address in the checkout page (which I wouldn't recommend, since they would get melted food or just bad food. But still someone might do it and I would like to avoid having to deal with such a problem.

It would be nice to be able to create the information filling side (delivery address, contacts) of the checkout and then let shopify handle the payment process, which I think is the most delicate part. 

I'm really in need for a solution, help would be greatly appreciated! Thank you guys