Copyright in the European Union and geo-blocking: a work that is in the public domain can be published online free of charge in a Member State even if it remains protected in another Member State [pdf]
https://curia.europa.eu/site/upload/docs/application/pdf/202...
Other blog post:
CJEU clarifies when geo-blocking limits online copyright liability
https://intellectual-property-helpdesk.ec.europa.eu/news-eve...
I find these are often very readable and interesting.
This seems extremely problematic, depending on what "state of the art and effective" means. It seems like blocking VPN users is unfortunately still on the table, as are other invasive enforcement methods.
This isn't codified into law for good reasons. Technology shifts and you don't want to have to update laws every time someone invents a new cipher or protocol.
The website is defending itself from having to pay a fine because they're blocking VPN users. They require blocking VPN users to skirt around the extreme terms in Dutch copyright law. If they didn't block VPNs, they would've lost already.
This boils down to "did they try hard enough not to violate copyright in the place(s) where copyright was still applicable".