I guess that depends on one's definition of "deal with" -- In Mr. B's case, I took it to mean "would have guaranteed this event would never have happened," which I think is an unrealistic benchmark since no law can reasonably provide such a guarantee ...

You seemed to characterise his stance more widely before when you reasoned that “Acts such as murder, rape... are all against the law, yet people still commit those crimes”.

Murder is the crime but the proposed legislation is about gun control and someone can break a regulation on that without committing murder. B was right therefore to expect any legislation offered as a solution to mass murder of children and teachers in a schoolhouse to actually inhibit the crime.

It’s doubtful that the legislature has any power to withhold a true constitutional right at any rate without widespread public support that makes it possible in fact. In general the least requirement for attempting to do so should be that its wider purpose ‘would’ be fulfilled and that enactment would confer a greater benefit objectively assessed than that which it withholds.

So appalling are these crimes that I was, as you know, content to replace ‘would’ with ‘could’ but only with the ‘balance of benefits’ criterion as part of the justification. I take the view, however, that the Obama administration is barking up the wrong tree by relying on legislative solutions to this problem. It’s unlikely you’ll ever get to firearm restrictions as stringent as those in the UK but even they didn't prevent the massacre that occurred at Dunblane in 1996.