Bug in RENAME TO?

I notice you can use most of the RENAME TO commands in postgres to 
rename system objects.  Renaming a system table is disallowed:

test=# alter table pg_namespace rename to blah;
ERROR:  permission denied: "pg_namespace" is a system catalog

But mucking with any other system object is not:

test=# alter function abbrev(inet) rename to bad;
ALTER FUNCTION

Is there logic in that?

Also, what about when I implement ALTER OWNER for everything?  Should 
that be banned on system objects?

Chris