This error has been seen in both survival and creative game mode, however, was first noticed in survival.

The world spawn was moved to the origin (x 0 z 0) using the /setworldspawn command. The spawn protection worked all day. The only person on the server who could correctly modify the spawn point on the server was myself. I needed to do some testing with the spawn protection and deoped myself. I was still able to modify the spawn point despite my deoped status. I restarted my client and the server. I was still able to modify the origin. I asked a third party to come to the origin to attempt to modify it. A player who has never been oped was able to modify the spawn point. I reapplied the /setworldspawn command. This re-enabled the spawn protection for that player, however, I was still able to modify the spawn point despite no longer being oped. I checked the original spawn location to see if the spawn protection was being applied there, it was not. It seems as though there is no spawn protection being applied. There is no one else currently available to do more third party verification of this issue on my server.

Potentially useful information:
Op-permission-level=4
spawn-protection=16
level-seed=-3088253498946039237
Map was originally generated using version 1.7.1