First lets be clear, this is not a discussion about arms control. I don't believe, nor do I think many others do, that there should be nukes on sale between the beer and condoms at the gas station. Thus I believe there should be some type of limits on what weapons should be possessed by the citizens. Nor is this a debate on the 2nd amendment and what it says. I try to stay away from anything in the constitution but 4th amendment probable cause crept in.
You're standing at the sink doing dishes occasionally glancing out the window to enjoy the migratory birds frolicking in the front yard. Suddenly the birds scatter in the wake of a four year old girl darting through the lawn rapidly loosing ground to a couple of ten year olds waving stick in hot pursuit. One trips the little girl, then both begin to beat her with their sticks. Now you a choice to make.
I would argue that in the above example, assuming you are capable, your are morally obliged to take immediate action. If the little girl was injured, I'd guess that most, even if incapable of action, would feel guilt over their lack of intervention. The difficulty lies in how much "action" is appropriate. Clearly tossing a grenade in the yard to stop kids fighting is a bit much. Which leads to the idea of the least amount of force to stop the little girl from being hurt (Minimum Necessary Force). Some might argue that a step wise progression of slowly increasing force: talk, plead, yell, get between, physically restrain, incapacitate, ... Clearly, the necessary action is greatly dependent on the situation. For instance if the boys were wielding knives, then talk, plead, yell, get between might be foolhardy at best. Or if they had a gun to the little girls head, any physical action might be hopeless. So set the definition of appropriate action aside for a moment and just assume there exists such an action.
Let's change the perspective. If you were the little girl and as you ran across the yard you notice a bat standing on the front porch. Is it alright to pick it up to defend yourself? If you say yes then it leads to other questions:
To come to any logical conclusion, on just about any topic, one first must decide on the facts or truths. If you plan to convince more than one person of the conclusion there must be agreement about the postulates. For with no base agreed premises, discussion is just air. I'll assume it's mostly Americans who are reading this and so for the first postulate or truth I present The Declaration of Independence. In particular
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness. — That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed, —Just to make sure all are on the same page some definitions are offered.
Our 2nd postulate: There exists people in the world, country, state, city, perhaps next door, who feel their Life, Liberty, and Pursuit of Happiness trumps mine. But from postulate one, I was endowed with these rights and so mine getting trumped is wrong. The question is who should stop it.
But first lets take the rights in order and consider how another may trump our right. Perhaps that will lead to who should insure it. For life the first is fairly obvious: Someone kills me. But from our definition it's more than that. Stopping me from growing and reproducing should also be included. I think we can agree that mutilation even if short of killing should be included. What ever you decide is the proper definition of life, someone who stops Life is not going to be subtle. Conclusion: someone should stop someone or somemany who are trying to kill someone or somemany. Deep huh.
What about liberty? Now this could be very subtle. On the other hand it clearly can not be absolute for then one could take the Life of others. Conversely, it could be argued that the latter part of the Pursuit of Happiness definition springs from the requirement that others have a right to Liberty. The key, of course, is in words, "oppressive restriction," which leaves quite a bit of wiggle room. Either way to clearly define taking of ones Liberty requires a more specific enumeration of "one's way of life, behavior, or political views." From the rest of the document it's clear that authors were more worried about "governments" taking away liberty than they were the next door neighbor which is why our definition has, "imposed by authority." I would argue an individual or group can have their Liberty restricted by another group or individual. Kidnapping would be could example. Many crimes might be an infringement of someones liberty but each would need a specific definition which isn't work the effort for my point.
First lets be clear. The protecting the Pursuit of Happiness does not mean ensuring everyone is happy. We are ensuring actions not feelings. More precisely, it's the freedom to do or not do. There is no preposition that what you choose to do will actually bring you happiness, but only that you may choose. Thus the government is obligated to ensure you have choice but not to insure your choices. With this in mind it's clear that things like choice of mate, religion, or who to support for political office should be protected. Someone or many could physically force the practice of a religion, but outside physical force we end up in discussions of economics or sociology which I'll avoid.
So far we've enumerated or obviously should have several someones or somemanys who the people need protections from: Other Governments, Our Government, Citizens singular or as a group, foreign citizens group or singular. Other Governments are clearly the responsibility of our Government to do the protecting. Similarly foreign citizens in other countries are the Governments responsibility. That leaves our Government which perversely our Government protects us against and other citizens. Now some would argue that the Government also must protect us from other citizens. And laws do that to some extent. Well they do if postulate two, some people are bad, wasn't true. But think about that, if the government puts enough restraints on the citizens to ensure it is impossible for anyone to commit a crime, infringe on anothers Life, much less Liberty or Pursuit of Happiness, then all the citizens have had at the very least their liberty greatly diminished.
I can hear you saying but that's what the police are for. Are they? The police in this country can only act against a Citizen when there is probable cause: the officer saw the crime committed, there is a reasonable basis to believe a crime was committed and the citizen arrested committed it, a judge issues a warrant. Note all three conditions are after a crime has been committed. At best they stop the criminal from immediately committing another crime but do nothing to stop a crime.
Another option would be to have enough police, body guards, to ensure no citizen has their rights infringed. How many cops will that take? 10% of the population? More if we are worried about domestic violence also. The average house hold size is 2.54 which means one in three need to be police. But wait that means 33% of the population is authorized to use physical force to protect them selves. So if one of those happens to be from the class of folks from postulate 2 then what?
Thus if a government is going to protect both the Life, Liberty, and Pursuit of Happiness of it's citizens, it must also recognize the right of the citizens to protect, using physical force if necessary, their own life at the least and probably their Liberty as well. However, protecting your own life requires a certain amount of training. But even with training half the population remains at a distinct disadvantage. The average women weighs 166 lb while the average male weighs 195. If the women was an elite body builder she could bench around 221 lb while most of a high school football team can bench more than that. If you talk about those who haven't trained or just started the women would bench 45 and the man 132 according to strengthlevel.com. Since only about 20% of the population trains that means on average men are about 2-3 times as strong as the average women. Men on average overtake women by 5 inches of height and thus have longer reaches. We still haven't considered the population which are elderly or disabled in some way. Clearly they exhibit even a greater disadvantage when protecting themselves physically.
Discrimination - unjust or prejudicial treatment of different categories of people. If self defense is legal then personal weapons allowed to be owned and carried by citizens should be the least lethal that still avoid discrimination. Clearly any weapon driven by mussel power and mass won't suffice. There are certain categories of citizens where this is impossible: blind.
Mace often reported as the nonlethal equalizer, but 20/20 did a story in 1981 where the Ventura Sherrif Department put mace to the test using 12 women licensed to carry and 4 deputies. Despite the women knowing what was coming none were effective in stopping a purse snatching. Here are more details. I've not experienced a full blast of mace or pepper spray, but in the early 80's there were 10-20 of us. All males, may have been a bachelor party; I don't recall. We were wondering around the bar district mostly acting foolish and as large groups of drunks will do, we were strung out a bit while walking to the next bar. In front of me I heard some yelling. A few more steps and my view cleared. Matt (not real name) was face to face with a bouncer screaming. I moved to grab Matt with the intent of dragging him away, when a police officer unleashed a blast of mace into Matt's face. Matt screamed a few explicatives apparently unaffected by the mace, so the cop discharged again. The second splashed me pretty well and by this time several other of our party had arrived and they helped me drag Matt away. My eyes were uncomfortable and the skin on my face burned. It took Matt about 5 minutes. We were already seated in the next bar before he began to cuss about his eyes burning. So my opinion mace will only stop someone who is super sensitive to it or who wants an excuse to stop. Mace also has a very limited rang: 10-15 ft.
Tasers: Tazers only fire once. Currently civilians are limited to a range of 15 ft and police versions have a range of 30 ft. A study in Orange County in 2011 showed the first shot to be 20% effective but went up to 92% after the second shot. Unfortunately the non-lethality of the weapon decreases repeated shots. According to the report they worked well for apprehending a fleeing suspect. The need to reload after every shot is a serious disadvantage for a defensive weapon. Especially because the typical civilian is suprised when the need for employment arives. Unlike law enforcement who are the initiators of the confrontation.