[CentOS] Centos User Privileges.

Hi list,
I've installed C 7.1.1503 and I've noticed that simple user can run from 
bash shutdown -h now/reboot without getting special permission (sudo, 
su). The machine is a VM without GUI (tested also on physical machine).
 From reddit I've got a suggestion: removing/comment out "-session 
optional pam_systemd.so" in /etc/pam.d/system-auth the problem is solved.
This is a bug?
If not, why use this policy? There are security implication?

Thanks in advance.