Limiting user from changing its own attributes

Hi,

In PostgreSQL a user can alter itself to change its user level parameters.
e.g. I can alter the user to change work_mem -

psql -U user1 -d postgres
postgres=# alter user user user1 set work_mem to '1024000';
ALTER ROLE
postgres=#

Is there a way I restrict this behavior? or atleast put a restriction on
the certain parameters e.g. work_mem to be not set to too high?

regards
Sameer