It is possible by many ways, the simple is to use chattr command. If the new user is to be created in Linux, at first it will redirect to the /etc/passwd file. So if that file is restricted to access using chattr command, either root user or the user with sudo access cant able to add the new user....

# chattr +i /etc/passwd

This command will restrict the access to create new user... To revert back run the same command by replacing with -i