[esbranson]

I believe this is covered by RFC 6092's REC-49 from 2013.

           Internet gateways with IPv6 simple security capabilities MUST
           provide an easily selected configuration option that permits
           a "transparent mode" of operation that forwards all
           unsolicited flows regardless of forwarding direction, i.e.,
           not to use the IPv6 simple security capabilities of the
           gateway.  The transparent mode of operation MAY be the
           default configuration.