I have been working as a tutor in the Writing Center at the local university for the past seven years and I can tell you that the presence or absence of commas makes not a hill of beans worth of difference in what the phrase actually means. The fact that militia and people are used interchangeably, with or without commas, should lead any clear-thinking person to conclude that the security of a free state depends on the militia, composed of all able-bodied men, whether in wartime or peacetime, having the right to keep and bear their own arms, which cannot and shall not be infringed.