§ 01
Definition
Most countries require network operators to be able to intercept the traffic of a named target when a court or authority orders it. In Europe, technical interfaces for this are standardised by ETSI.
§ 02
How it works
An authority serves an order on an ISP or provider, which then copies the target's traffic or metadata to the agency. Encryption limits what an ISP can hand over: if you use a VPN, the ISP sees only encrypted traffic to the VPN server, and the demand would have to go to the VPN provider.
§ 03
Why it matters
This is the core of the jurisdiction question for VPNs. The provider's home country decides what it can be ordered to intercept or log going forward, which is why audits, RAM-only servers and transparency reports matter.