A requirement the spck.dev suite checks on UCP servers. The quoted text is the normative requirement; the citation links to the exact line of the pinned spec source it was taken from.
Implementations MUST reject URLs dereferenced during identity resolution that resolve to special-use IP addresses (RFC 6890 loopback, link-local including the cloud-metadata address 169.254.169.254, private, and other reserved ranges), except a loopback target when the verifier itself runs on the same loopback interface (local development).
A deviation on a MUST fails the run and shows the requirement next to the actual response. Checks the suite cannot validate soundly are reported inconclusive or not-tested — never a silent pass. The full verdict semantics are on the grading rubric.
The hosted check covers the read-only surface; the CLI and GitHub Action run the full suite, including this check when your store declares the capability it belongs to.