Firstly: VPNs exist
Secondly: That would involve logging user IPs, or at least what country they're accessing the site from, so no.
Not even. Assuming the web server is backed by NGINX for example, you could have GEO locations defined which would redirect traffic from specific ASN subnets to anywhere you choose. Allowing those on the VPN or those in the allowed region to have access.
This happens at a level below the authentication and doesn't add any real levels of overhead.
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