Where is $#local syntax using allowed?

[Sciurus]

I add some rulles to LOCA_RULE_0 to redirect mail from dnsbl-relays
and from some other relays (matched to my regex map) to local mailbox.
It works well.
Now I am going to post these rules to my sendmail-page but I need some
theory about using
$#mailer because I is often asked about redirecting to local or
remote mailbox (not quarantine) mail based on Subject or other
header's content. So in my page I would like to accentuate
particularly this impossibility.
It will be splendidly if I shall be able to refer to opinion of
Sendmail Guru because docs doesn't explicitly clearify this point
(imho).

I have read op.me carefully and spent a lot of time on
comp.mail.sendmail seeking the confirmation of imposibility of using
mailer local or esmtp in rulesets other than 0 (and subroutine of 0)
and 5 (only local?), id est in the check_(relay|mail|
rcpt),Check(Subject|Received|MessageID|etc). But I found out only the
following in the op.me
"The $# syntax should only be used in ruleset zero, a subroutine of
ruleset zero,
or rulesets that return decisions (e.g., check_rcpt).",
"Rule set 0 is one of the few rule sets that may use $# ...Rule set 5
can also return a $#" (Sendmail book)
and recomendation to use procmail or milter to redirect mail based on
Subject content (comp.mail.sendmail).
But "rulesets that return decision" may use only error or discard
mailers, doesn't they?