Simply put...they're law enforcement officers. Simply declaring something secure (please, let's not get into the effectiveness or lack thereof regarding security screening) doesn't make it so. No system in existence can provide absolute security. Most cops worldwide carry weapons, yet they are rarely used since most contacts don't result in deadly force. The weapons are carried so that LE can effectively respond in the event, however unlikely, that a deadly force scenario occurs. LE without weapons to adequately defend themselves and those they are sword to protect is rather pointless. Even countries like the that have historically avoided arming their police are yielding to the threats faced by their officers and are fielding armed officers in greater numbers.

TB