This is a guest post based on a paper that was presented at the 2023 Firearms Law Works-In-Progress Workshop. The Workshop is held each year on a home-and-away basis with the Duke Center for Firearms Law.

In 2021, Professor Adrian Vermeule published “Common Good Constitutionalism,” which advocates for an interpretive framework grounded in the natural law and oriented to the common good. While the idea that law should be interpreted in light of its background natural law principles is not new, Vermeule’s work pushed the ongoing debate between positivist originalism and the natural law into the spotlight. Obviously, Second Amendment jurisprudence of the last two decades has been grounded in originalism. So this blog post—and the paper it summarizes that I recently presented at the 2023 Firearms Law Works-In-Progress Workshop—asks the question: what would a shift to a natural law interpretative framework mean for the Second Amendment?

The classical legal tradition begins with Aquinas’s definition of law as “an ordinance of reason for the common good, promulgated by a public authority who has charge of the community.” This definition is deceptively complex, and this blog post is short, so let’s focus on two aspects of the definition. First, an ordinance (the positive law) must be “of reason.” Or, to put it another way, it must be consistent with and derived from those natural principles that we are able to ascertain by reason (the natural law). Second, the ordinance must be “for the common good.”

The natural law provides general principles of obligation that we are theoretically able to reason to—sometimes as broad as “do good and avoid evil.” While these principles are binding in their own right, they are often under-determinate as applied to concrete situations. A classic example is speed limits: the natural law may provide a general principle that people should refrain from acting in a way that endangers innocent lives, but does this mean that a residential speed limit should be 20 MPH or 30 MPH? Neither speed is required by the principle, but both are consistent with it, and so lawmakers are free to pick one and either decision is consistent with natural law. This determination is not unbounded, but is constrained by the natural principle behind the speeding law. This narrowing function applies not only between the natural law and positive law generally, but also between hierarchies of positive law. A constitution may partially determine a natural principle, but leave room for further determination by legislation, and so on with agency regulations. Each step of determination narrows the scope of further possible determination, with regulatory decisions constrained by legislative principles, legislation by a constitution, and a constitution by the natural principle itself.

Law must also be oriented to the common good. This does not mean, however, that a law must merely provide some public benefit. Instead, the common good is that good that harmonizes the interests of the individual with that of the community, giving to each their due so that they can flourish individually and have the resources to contribute to a flourishing community. This common good requirement is not wholly distinct from that of consistency with natural principles described above. Instead, a law that is oriented to the common good must apply the natural law principles that provide for a just ordering of society.

So, in practice, a classical legal interpretation takes into account these features of law. It begins with the text of the law, discerning the fixed linguistic meaning of the text in order to ascertain the determination made by the lawmakers. In many cases, this provides the answer in any given case. However, where the text is under-determined as applied to the facts of the case, the higher order principles of the law would be considered. In the case of legislation, this means looking to the text of the constitution to ascertain the higher order determination. For constitutional text, one would trace the law back to first principles in order to figure out its application.

This leads naturally to the question: what higher-order principle applies to the Second Amendment? As usual, the text proves helpful. Specifically, the prefatory clause invokes ideas of the militia and the security of the state, suggesting that the Second Amendment was intended to determine a principle of defense. Under the classical conception, this principle had three aspects or variations. The first involves self-defense against threats of immediate personal violence. Thomas Aquinas approved of self-defense where the intention was not to harm another but to save one’s own life; harm to the aggressor is an unfortunate but sometimes unavoidable side effect. Such self-defense must also be immediately necessary and performed using minimal force. This aspect of the principle is typically the focus today in cases like Heller and Bruen. Yet there is also defense of the community against foreign aggression. Just War Theory provides a complex set of rules for how this defense should be undertaken. Finally, there is defense of the community against an unjust ruler. As described above, law must be oriented to the common good—and nothing is more antithetical to the common good than tyranny. Classical legal thinkers recognized this and thought it lawful for citizens to resist governmental injustice. As Benjamin Franklin once noted: “Rebellion to tyrants is obedience to God.”

The broader defense principle then derives an individual good—personal self-defense—and a communal good—defense of the political community from foreign and domestic violence—in one harmonized principle. The individual nature of the personal defense aspect does not remove it from the sphere of the common good, just as a law does not per se support the common good by providing a public benefit. The common good harmonizes the interests of the individual and the community, rather than subjecting either to the other.

Reading the Second Amendment in light of this principle of defense yields certain bounds that constrain lawmakers’ determinations. While there may be room within the scope of the Second Amendment’s prior determination for legislation oriented to the common good, any such determinations must be tested for their compliance with the defense principle as narrowed by the Second Amendment. In application, the result is probably different depending upon which of the three circumstances of defense described above is applied. For example, personal defense may require the ability to bear in public an arm sufficient to repel a personal attack, but not more. In order to defend oneself against immediate harm, the tool of defense must be immediately available. Thus, to be oriented to the principle of immediate self-defense, a regulation should not stop a citizen from bearing arms in public of a type minimally necessary to defend against immediate personal violence. On the other hand, defense against foreign aggressors and unjust rulers may require allowing possession of arms sufficient to resist, collectively, a sovereign’s standing army. But the principle may not require allowing such arms to be carried in public. A similar sentiment was expressed in early American laws disallowing the carrying of arms in public “to the terror” of the public. So, a classical legal reading of the Second Amendment protects defense as a common good—defense of individual safety, as well as defense of the community, all in one.

While Supreme Court Second Amendment jurisprudence isn’t facially grounded in the natural law, its originalist outcomes are consistent with classical principles. This consistency begins with United States v. Cruikshank, the very first Second Amendment challenge to reach the Supreme Court. There, the Court recognized that the right to keep and bear arms “is not a right granted by the Constitution [nor] is it in any manner dependent upon that instrument for its existence.” Following Cruikshank, the Supreme Court developed two models of analysis for Second Amendment challenges: one focused on the collective right associated with the militia and defense of the community, and one based on the individual right of self-defense. In Presser v. Illinois and United States v. Miller, the Court upheld laws because they did not infringe on the right of the people, as the militia, to own “ordinary military equipment.” In Heller and later cases, the Court has turned its focus to whether a law infringes an individual’s right to bear arms for self-defense. This is not a break with past precedent, however. The Court has given a militia-based analysis to cases involving communal self-defense, and one grounded in the individual right where threats of personal violence are at issue. These are not opposites, but instead different sides of the same defense principle that has remained consistent from Cruikshank to Bruen.

A classical reading of the Second Amendment, then, protects the right of the community to defend itself as both a body and a collection of individuals. This right comports with the natural law principles of defense of self and community, and supports the good of both as a common good. The classical reading also reconciles the tension between the collective and individual rights of the Second Amendment, for they are both grounded in the same ultimate principle of defense.