re: I'm wondering.
I don't know the legal background, but there are probably court precedents in place on these Second Amendment restriction questions that are similar to the "fire in a crowded theater" situation in free speech.
It's obvious that restricting guns hasn't helped the crime rate in Washington DC, which had a murder rate that peaked in the 90s at about 81 per 100,000. As a comparison, the civilian death rate in Iraq for 2007 was somewhere between 82 and 88 per 100,000.
It's improved since then. I think the rate in D.C. is down to about 29 per 100,000 in 2006, which has more to do with stricter curfews, surveillance cameras, and other police crackdowns.