new and old not available in rule subselects?

It seems like you can not use the magical relations new and old in
sub-selects in rules. Why is this, or is there something I haven't
understood correctly about rules and new and old?

create table "user" (
username varchar,
created timestamp default now(),
detstroyed timestamp default null);

create table users (
time timestamp,
users bigint);

create rule user_insert_count as
on update to "user"
do also
select
new.created, (select count(*) from new where destroyed is null)
into users
from new;

ERROR: relation "*NEW*" does not exist

Thanks in advance,
Egil