Some of you may have seen this video but it is worth watching in light of recent events. It deals with gun confiscation in New Orleans after Katrina. The differences I see in a nation wide situation is it will be harder for authorities to cover every county, city and state without being spread very thin and therefore being extremely vulnerable.
Watch this with the perspective of how you would react and notice the mistakes some of these made due to being caught off guard.
Learn from history.