aclitem binary encoding

Hi all,

I was using a PostgreSQL driver that used binary input/output to query
some ACL data and was surprised to see the following error:

    no binary output function available for type aclitem

In fact, aclitem has no binary input or output functions

    postgres=# SELECT typinput, typoutput, typreceive, typsend FROM pg_type WHERE typname = 'aclitem';
     typinput  | typoutput  | typreceive | typsend
    -----------+------------+------------+---------
     aclitemin | aclitemout | -          | -
    (1 row)

Is this an intentional decision to not support a binary encoding for
aclitem types? Or is it just a lack of a feature?

Thanks,
Joe Koshakow