Public Law & Legal Theory Research

Second Amendment “arms” jurisprudence is a muddle. Lower courts have been obliged to craft various approaches from Supreme Court decisions that appear to point in different directions.

We propose that the scope and protection of Second Amendment “arms” could be calibrated to a single, shared metric across all weapon types–lethality. Lethality captures the issue that everyone cares about: whether one advocates for gun rights or for gun violence prevention.

Lethality helps make legible the changes in weapons technology over time and explains the principle that underlies traditional regulation of “dangerous and unusual” weapons. The more lethal a weapon is, the more dangerous it is. And focusing on lethality helps sweep away the distractions that currently beset Second Amendment adjudication over arms, like whether a particular feature of a weapon is cosmetic or functional, whether a particular weapon is sold more often than pickup trucks, or whether any given weapon technology “descends” from another.

Part I of this article explores the various formulations of the scope and coverage of Second Amendment “arms” and how the current framework fails to function as a workable doctrine.

Part II explains how lethality as a common metric can help harmonize the different approaches.

Part II.A. offers a historical approach to indexing lethality across different weapons and different times, relying on the research of the military historian Trevor Dupuy. Dupuy, working under the auspices of the United States government, developed an index with which to compare the lethal capacity of different weapon platforms across time. His “Theoretical Lethality Index” reduced to a single number the lethal capacity of weapons as varied as swords and nuclear warheads. Hence, one could with this number compare the lethal potential of a person wielding a musket versus a machinegun.

Part II.B. supports this historical methodology with experimental data measuring the lethal potential of historical and contemporary technology. By firing rounds of different types and calibers from different weapon platforms into gelatin and measuring the kinetic energy released, and then by multiplying that kinetic energy by rates of fire, biomechanical researchers can provide apples-to-apples comparisons of the lethal capacity of different weapons from different eras.

Part III explains how this data on lethality relates to the historical principles of this Nation’s tradition of weapons regulation. Specifically, this part shows how regulations that target mass violence, govern storage of dangerous materials, or that prohibit commonly owned but “dangerous and unusual” weapons can be informed by this historical and experimental data on lethality.

This historical and experimental data offers a consistent, replicable metric from which to determine the lethality of different weapons systems. It supplies an empirical accounting of whether, as New York State Rifle & Pistol Association, Inc. v. Bruen stated, transformational technological change has taken place that justifies a “more nuanced approach” to historical analogues regulating “dangerous and unusual” weaponry. It also allows Second Amendment doctrine to tether the “principles” behind a historical tradition of regulation to something concrete, measurable, and falsifiable; rather than trap Second Amendment rights and regulation in the technology of the past.

Miller, Darrell A. H.; Tucker, Jennifer; Rutland, Peter; and Hargarten, Stephen, "Lethality And The Historical Principles Of Arms Regulation" (2026). Public Law and Legal Theory Working Papers. .
https://chicagounbound.uchicago.edu/public_law_and_legal_theory/986