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