overriding user defined functions with the same name as system commands

This function exists in one of my users' ~/.bashrc:

function rm()
{
        ls $*
        echo "rm?"
        read ans
        if [ "$ans" == 'y' ]; then
                /bin/rm $*
        fi
}

In my ksh script that users are required to run, I have a line like this:

[[ "$KEEP" = "" ]] && \rm $FILE

While the backslash escapes user-defined aliases, it does not stop the script from running user defined functions with the same name. As a result, my user's rm() function is called instead of the system function.

I found this superuser question question & response, but the resolution only applies to a builtin function, not a system command.

What's the best to enforce the rm command from being called, and not an alias or function? Must I specify the full path to rm and every system command that I want to ensure is executed correctly? Is there a better way?

You can use command to circumvent the normal bash function lookup.

command rm

Non-destructive example:

$ alias which='which -s'
$ function which { echo "which $@?" ; }
$ which which
which -s which?
$ command which which
/usr/bin/which

Alternatively, call it using env (executing the first program with the given name on the $PATH, or by specifying the full path.

/usr/bin/env rm
/bin/rm