Refusing sales to a certain postal code

[superprg]

Just realized. Unfortunitely, it won't change anything if people were blocked by entering specific zip codes or postal codes, since they could simply enter any valid values and would still be able to checkout the orders. Meaning, nothing would actually prevent these users to pass through.

If you wish to restrict specific access, you should do so by .htaccess with IP address prefixes (or by domain name is also possible).

How can that be done?
Mind elaborating?

Also, is there no service which can actually map the zip code with the IP address and then let you you know if the zip entered is right or not? ...just a thought