Restrict product availability to certain languages/countries in Commerce
I am assuming you have shipping enabled for your site. In that case, you can add a country field to your product display, say "Unsupported countries". And while creating a product, you can chose countries for which you are not going to sell. On checkout, add a rule to compare this field's value and the shipping address and If the shipping country is one of unavailable country, show a message and re-direct to cart page asking them to remove this product from their cart.