How to prevent sudoers users not to run restricted sudo commands after switching to root

Issue

1. We granted sudouser the right to run all commands excepted some administrative commands such as /usr/sbin/useradd, by this adding this entry in /etc/sudoers file :

sudouser ALL=(ALL) ALL, !/usr/bin/passwd root, !/usr/bin/passwd, !/usr/sbin/su, !/usr/sbin/su root, !/usr/sbin/visudo, !/usr/bin/vi /etc/sudoers, !/usr/bin/vi /etc/passwd, !/usr/bin/vi /etc/group, !/usr/bin/su, !/usr/bin/sudo su, !/usr/sbin/groupadd, !/usr/sbin/useradd, !/bin/chown, !/usr/sbin/usermod

2. But the problem is after sudouser switch to root by running command sudo -s, he can run any command as root which includes the restricted commands above. We do not want this to happen.