Anyone interested in this topic should watch the documentary zeitgeist. It addresses this topic as well as several other related issue. PLEASE check it out
I think the point is, regardless of WHAT exactly happened, the government who is bound by contract to protect us from foreign threats had the infrastructure in place to prevent this kind of thing, but for whatever reason, they failed to do so. If I fail to follow the same contract (federal law) I get fined, jailed, etc. ad absurdum regardless of my intent, but not many seem to believe that the government needs to be held to the same standard.