I don't post often but I figured I'd raise a few points, I apologize in advance for length- I like to be thourough. First, in the interest of full disclosure, I am a firearm enthusiast and have used small calibre rifles, higher gauge shotguns(12 +20) and air rifles that are qualified as firearms. I have a license to own and purchase non restricted fireamrs. I am also Canadian, so I think that mght give me a differing perspective on firearm regulation in a place that is not as liberal with such regulations as the United States. I am not sure exactly what the nature of firearms law in the United States is, from my understanding it is regulated mostly on a State to State basis, with a broad over -arching federal structure in place as well. In Canada, for purposes of comparison, our firearm ownership is regulated exclusively at the federal level by the Firearms Act and Criminal Code. There are three types of categories: non-restricted, restricted and prohibited. All levels require an extensive training course and mandatory registry of any firearms that are purchased. Non restricted firearms are basically hunting rifles(within a certain size), shotguns(within a certain size) and anything that fires a projectile at 500+ FPS(air rifles etc.). Assault rifles(if fully automatic) fall under the category of prohibited weapons. Nobody outside of law enforcement or military is permitted to possess them. We have no provision in our Constitution entitling use to bear arms or no similr specific section for it(as far as I'm aware).
(Source: http://www.rcmp-grc.gc.ca/cfp-pcaf/faq/index-eng.htm#a1)
My understanding of the debate over the Second Amendment is that it is rather complex, incorporating both vital legal principles as well as historical values that arose in the process of American Independence. I think it would be important to put down here the actual wording of the Second Amendment:
"A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed." (Source: http://www.law.cornell.edu/constitution/constitution.billofrights.html)
The leading case on the matter is District of Columbia v. Heller where the Supreme Court finally ruled on the nagging issue of the language and grammer used in the Second Amendment. The issue was whether the first comma implied a collective right of the people to own and bear arms as opposed to an individual right. The importance of this distinguishment being that if the right was collective, it would only be appropriate for an individual to bear arms in the process of being part of a militia whereas an individual right would entitle the indivdual, without prequisite membership in a militia, to keep and bear arms.
So, how is this related to the thread you ask? Firstly- the historical principle behind civilian ownership of arms in the United States arise out of libertarian concerns of government interference. Literally, back when the Constitution was made, it was considered a good idea for citizens to be armed to control the scope of government. I don't think you can blame their mistrust in government either- the King was pretty oppressive. Secondly, Heller, established something else- that the purpose of the Second Amendment was individual protection(self defence). Quoting the majority opinion here:
"The Second Amendment protects an individual right to possess a firearm unconnected with service in a militia, and to use that arm for traditionally lawful purposes, such as self-defense within the home".
So the question then becomes(from a more legal perspective), is the ownership of an assault rifle consistent with the purposes of the second amendment:namely self defence. A more philosophical question would be "self-defence from whom?" Is it still necessary to have an armed citizenry to curtail government? Does government even have the right to strip citizens of methods of resistance? Will the time ever come for the next American revolution?
I can't answer these questions, not without making this post even longer than it already is! For what it's worth, I don't think it is necessary for the purposes of self defence to have an assault rifle but I don't think the government should be able to cuurtail individual rights so as to prohibit their ownership. You can always heavily regulate it, or regulate the ammunition without denying the right of ownership. Sorry for the long post.