Permissions for foreign keys

I'm using 7.0 and have noticed that I need to grant SELECT and UPDATE
permissions on any referentially-related tables.  Can/should I get
around this?  A somewhat contrived example:

CREATE TABLE emp (id integer PRIMARY KEY,salary integer
);
CREATE TABLE proj (id integer PRIMARY KEY,emp_id integer REFERENCES emp
);
CREATE TABLE bill (id integer PRIMARY KEY,proj_id integer REFERENCES proj
);
INSERT INTO emp  VALUES (1, 100000);
INSERT INTO proj VALUES (1, 1);
INSERT INTO bill VALUES (1, 1);

GRANT ALL ON proj TO someone;

Connect as someone:
=> INSERT INTO proj VALUES (2, 1);
ERROR:  emp: Permission denied.
=> UPDATE proj SET id = 2;
ERROR:  bill: Permission denied.

It appears that I need to grant:  SELECT,UPDATE on  emp to UPDATE or INSERT into proj.    SELECT,UPDATE on bill to
UPDATEproj.  
 

When I grant these permissions, the above statements succeed.

If I don't want users to have UPDATE (or even SELECT) access on the
other tables (bill and emp), but I want referential integrity, what can
I do?

-- 
Rick Delaney