The Solid Web Access Control document describes a mechanism for ACL resource location discovery. That involves inspecting a Link header with the rel="acl" parameter.

That link relation, however, is not registered with IANA. Alternatively, many Linked Data specifications (LDP, LDN, OA) make use of IRIs for use with these sorts of discovery protocols. In the second case, an IRI could be defined in the ACL vocabulary without needing to register the relation with IANA.

More discussion of this issue is at solid/web-access-control-spec#21