There’s been a long standing argument by constitutional scholars about whether the second amendment referred simply to militias or it spoke to an individual right to possess arms. I think the latter is the better argument. There is an individual right to bear arms, but it is subject to common-sense regulation just like most of our rights are subject to common-sense regulation. So I think there’s a lot of room before you getting bumping against a constitutional barrier for us to institute some of the common-sense gun laws that I just spoke about.
One hardly knows where to start. First, I think even at Harvard Law School they teach that when fundamental constitutional rights (e.g. speech, voting) are at issue, government regulation must be more than merely “common-sense” (usually termed “reasonable” in legalese) in order to abridge that right. (Likewise, in the area of discrimination prohibited by the 14th Amendment the government may not merely offer a “reasonable” explanation for classifying citizens by race.) In most cases, statutes which implicate constitutional rights are evaluated under a “strict” scrutiny test, or at the very least, an intermediate scrutiny test (for example, in the case of discrimination on the basis of gender). To simplify, the government has to have compelling or very important reasons to violate a constitutional right, and the means must be tailored narrowly to meet the objectives. Next problem: usually an outright ban on a constitutional right, as was the case with the D.C. handgun ban, is not going to meet any heightened scrutiny test.