Function Anomaly?

All...

Given the following type and function:

CREATE TYPE getnote_t AS (nid BIGINT, ownerid INTEGER, ownername
VARCHAR, hostname VARCHAR,
entrytime TIMESTAMP, is_active VARCHAR, is_private VARCHAR, notetext TEXT);

CREATE OR REPLACE FUNCTION getnote(INTEGER, BIGINT) RETURNS getnote_t AS
$getnote$
SELECT n.nid AS nid, n.ownerid AS ownerid, o.ownername AS ownername,
n.hostname AS hostname,
n.entrytime::TIMESTAMP(0) AS entrytime,
'[' || (CASE WHEN n.is_private = TRUE THEN 'PRIVATE' ELSE 'SHARED'
END) || ']' AS is_private,
'[' || (CASE WHEN n.is_active = FALSE THEN 'INACTIVE' ELSE
'ACTIVE' END) || ']' AS is_active,
n.notetext AS notetext
FROM notes n, owners o
WHERE (CASE WHEN (n.ownerid != $1 AND n.is_private IS TRUE) THEN FALSE
ELSE TRUE END)
AND n.ownerid = o.ownerid AND n.nid = $2
$getnote$ LANGUAGE SQL;

When I call it with a row where n.is_private is TRUE and n.ownerid IS
TRUE, I receive a single row of all null values:

notesdb=# select * from getnote(1, 2);
nid | ownerid | ownername | hostname | entrytime | is_active |
is_private | notetext
-----+---------+-----------+----------+-----------+-----------+------------+----------
| | | | | | |
(1 row)

When I submit the query directly (getnote.sql is simply the query with
the CASE statement forced to false):

notesdb=# \i getnote.sql
nid | ownerid | ownername | hostname | entrytime | is_private |
is_active | notetext
-----+---------+-----------+----------+-----------+------------+-----------+----------
(0 rows)

Thanks very much in advance for any insight you can provide.

-- Gary Chambers

/* Nothing fancy and nothing Microsoft! */