Disable TRUST authentication by using ClientAuthentication_hook

I'd like to disable the TRUST authentication method for certain servers
where modification of pg_hba.conf and restarting a service is fairly easy
for a number of users.

I looked at this example
https://wiki.postgresql.org/images/e/e3/Hooks_in_postgresql.pdf It appears
that creating a ClientAuthentication_hook and call ereport(ERROR) in case
that Port->HbaLine contains TRUST would do the job. Is that right?

I am aware that this would not make the server entirely secure but it would
make it at least a bit more difficult to enter.

Thanks Klaus