FreeBSD 6.3-PRERELEASE unable to change file permission

[Anjang Aki]

hi!.. i'm not able to change file permission to disable rlogin and
login on my box even as root

# ls -lo /usr/bin/login /usr/bin/rlogin
-r-sr-xr-x  1 root  wheel  schg 19996 Dec  1 13:04 /usr/bin/login
-r-sr-xr-x  1 root  wheel  schg 10140 Dec  1 13:04 /usr/bin/rlogin

# chflags -R nouchg login rlogin
chflags: /usr/bin/login: Operation not permitted
chflags: /usr/bin/rlogin: Operation not permitted

# chmod a=rx /usr/bin/login /usr/bin/rlogin
chmod: /usr/bin/login: Operation not permitted
chmod: /usr/bin/rlogin: Operation not permitted

it makes me uneasy as my users can still use login and rlogin to gain
access to the box

my system:
# uname -a
FreeBSD k3.college.edu 6.3-PRERELEASE FreeBSD 6.3-PRERELEASE #1: Sun
Dec  2 18:51:02 MYT 2007     root at college.edu:/usr/obj/usr/src/sys/EDU
 i386

thanks for advice

-- 
-- Anjang Aki --