These proposals are carefully and narrowly drawn.
Haller notes that it wouldn't be a crime, for example, to allow someone who is merely depressed to have access to your gun. If that person were depressed and torturing animals, on the other hand, the reasonable-cause threshold might be met.
Haller is staying out of the fight over the assault-weapons ban, which he fears will achieve nothing because it polarizes Congress and excludes so many kinds of guns. He developed his ideas in consultation with school-security and law-enforcement professionals.
He also drew on a federal report issued after the 1999 Columbine High School shootings, which found that targeted violence at schools rarely results from sudden impulses and that others usually have some idea of the attacker's plans.
The reporting requirement is designed to increase the chances that information gets to the authorities.
The proposals don't restrict the rights of responsible gun owners, and they aren't attacks on gun culture.
Instead, they seek to strengthen norms - like the norm that firearms should be secured - that are already present in that culture. So they are more politically viable than most gun-control proposals, and more likely to achieve practical success, as well.
At the same time, they don't follow the template of the National Rifle Association. They don't assume, that is, that the only solution to the problems caused by bad people with guns is good people with guns.
There is room for debate about what level of government should put these reforms in place.
Haller points out that in a time when kids could be reading disturbing messages from chat-room friends across the country, it might make sense to have a national hotline where such instances could be reported - especially if threat-assessment experts were available there.
One maddening feature of the gun debate since the Sandy Hook massacre is how disconnected the public discussion has been from what actually happened there. So many proposals would have changed nothing even if they had been implemented.
It seems much more plausible that the ideas in Haller's memo might have made a difference at Sandy Hook or Columbine or Virginia Tech.
And the Pozner family's ability to make a constructive response to grief and horror should fill us all with awe.
Ramesh Ponnuru, a visiting fellow at the American Enterprise Institute and a senior editor at National Review, is a Bloomberg View columnist.