Hays Parks on the Means and Methods of Warfare

by , | Oct 20, 2021

Hays Parks Weapons Review

Hays Parks was one of the leading voices of the United States’ view of the law of war over the last 50 years, and one of the founding fathers of the field of operational law in the U.S. military. Both of us are honored to have either worked directly with him or to have followed in his footsteps.

As this symposium highlights, Parks heavily influenced the U.S. view of the law of war through his writing and scholarship. His work on the means and methods of warfare, specifically with respect to munitions, however, is the subject of our present article. In particular, we focus on three areas where Parks’s work has had a notable impact. First, we examine his emphasis on the need for legal advisors to understand the science and technology behind weapons. Second, we highlight the importance he placed on ensuring the law remains practical. And finally, we review his conviction that law of war practitioners can make significant contributions to the field by writing.

Understanding the Science and Technology of Weapons

Those who are familiar with Parks’s work know that much of his efforts focused on weapons and munitions. Undoubtedly, his interest in the employment of weapons in combat dates at least to his own service in Vietnam from 1968-1969 as an infantry officer and senior prosecuting attorney for the First Marine Division. In at least one article, he refers to controversy surrounding weapon use in Vietnam, highlighting the “new, smaller-caliber (5.56x45mm) M-16 rifle, napalm, cluster-munitions, flechettes, blast (high explosive) munitions, and so called ‘plastic fragmenting munitions.’” One must also imagine that as a junior officer in Vietnam, Parks was personally acquainted with their use in combat. This familiarity, and the imperative for legal advisors to understand the technology behind weapons and munitions, permeates many of Parks’s articles.

One practical example, with which generations of U.S. military attorneys are familiar, is the catalog of “Memoranda of Law” he authored and that were published in The Army Lawyer. These memorandums were generally legal reviews of weapons systems or reviews required under various Department of Defense or subordinate service regulations. Some examples of these memoranda include: Use of Expanding Ammunition by U.S. Military Forces in Counterterrorist Incidents, The Use of Lasers as Antipersonnel Weapons, Review of Weapons in the Advanced Combat Rifle Program, Sniper Use of Open-Tip Ammunition, and The Joint Service Combat Shotgun Program.

Not only was Parks one of the few lawyers writing in depth on weapons—without question, his assignment as the U.S. Army’s Law of War expert provided unique access and interest—his writings underscored the value of ensuring lawyers understand the technology and terminology associated with weapons. For example, in his Memorandum of Law—Review of Weapons in the Advanced Combat Rifle Program, Parks discusses ammunition casing, jacketing, bullet weight (in grains) and diameter, and muzzle velocity. As Parks makes clear in this memorandum and others, a lawyer must understand these various terms and their relation to how the bullet is chambered, fired, travels to its target, and impacts its target. These factors are critical to making the legal determination whether a particular weapon causes unnecessary suffering or is inherently indiscriminate. They also make clear why DoD-approved munitions—despite the claims of some—are lawful for their intended use.

Another such example is the use of open-tip ammunition. This bullet has “a shallow aperture (approximately the diameter of the wire in a standard size straight pin or paper clip) in the nose of the bullet,” and has been used for decades for marksmanship because of its superior accuracy at long distances. Some, including even Army judge advocates serving in Iraq in the early days of Operation Iraqi Freedom, believed the open-tip of the ammunition was actually a “hollow-point” bullet designed to expand on impact. In his seminal review of MatchKing open tip ammunition, Hays Parks explained that the open-tip provides “a bullet design offering maximum accuracy at very long ranges” and was not intended to expand or flatten easily on contact with the human body.

Parks’s works provided a foundation for appreciating the important science behind our weapons. Perhaps more importantly, he routinely emphasized that military lawyers must also understand how weapons are actually employed by the warfighter.

Ensuring the Law Remains Practical

Hays Parks’s service as an infantry officer in the Vietnam War certainly gave him firsthand experience with how weapons are employed on the battlefield. Many judge advocates, on the other hand, have not served either in a combat arms branch or in actual combat. This lack of practical experience makes it all the more important that military attorneys work to develop an understanding of how weapons are actually used in battle.

In his Memorandum of Law: Trauvax Preparatoires and Legal Analysis of Blinding Laser Weapons Protocol, Parks insists that judge advocates must understand the “means” and the “methods” of warfare, and recognize the difference between the two. He weaves this theme throughout the memorandum and provides examples that highlight why an actual understanding of how weapons work—rather than blind speculation—is critical, whether to negotiating weapons treaties or to advising tactical commanders in combat. According to Parks, these insights helped shape the protocol on blinding lasers. The United States was able defeat the push for a complete ban on lasers because it emphasized their practical use for range-finding, target acquisition, and target designation—uses that help minimize danger to civilians in targeting. The final protocol prohibited only those weapons that were specifically designed to cause permanent blindness to unenhanced vision.

Parks’s review of the Joint Service Combat Shotgun Program includes another example of the importance of understanding the practical use of a weapon in combat. In this work, Parks not only provides the reader with a detailed history of the use of shotguns in military history, he also explains why their use in combat is lawful, particularly with regard to superfluous injury. Parks walks the reader through the effectiveness of the shotgun at close ranges compared to high-velocity rifles, and he describes how they can diminish the risk of injury to civilians.

Parks also explains—as he does in several of his articles—how the weapon wounds. By doing so, he explains why buckshot, a projectile that can cause multiple wounds, is not illegal. He also describes why lead-and-antimony buckshot, although capable of flattening, is not designed to flatten easily or intended to cause excessive injury. Once again, his no-nonsense, practical approach to the intended operational use of a weapon is not only instructive to the practitioner in the field, but also serves as a model for how military attorneys should understand their clients’ arms.

Contributing to Legal Understanding through Writing

The final aspect of Hays Parks’s contributions to understanding the use of weapons in war is his writing itself. Dating back to at least the late 1970s, Parks published dozens of articles on all manner of subjects related to the law of armed conflict. At a time when the number of published articles, blog posts, and podcasts on the law of armed conflict has increased exponentially, especially since 2001, it may be easy to forget the singular influence Parks had on practitioners of the relevant law, policy, and practice in the field. Although much has changed in the decades since he joined the Army’s Office of the Judge Advocate General, the need to publish informative and critical analysis of the law has not abated. It is even more important now.

LTG(Ret.) Charles N. Pede, who recently served as Judge Advocate General of the Army, regularly encouraged the Corps to “flood the zone” by publishing articles that describe the law as it exists and how we implement that law in actual practice. Law of war practitioners, both civilian and military, must emulate Parks’s example and engage with our partners, academics, and civil society by sharing what the law is (lex lata), not what some want it to be (lex ferenda). Parks was a strong voice in countering misunderstandings—and even outright falsehoods—with respect to the means and methods of warfare. Actively stating practitioners’ view of the law not only helps bring clarity to the law, but informs our junior judge advocates, many of whom do not have significant operational experience, on the law and how to apply it in practice.


In conclusion, W. Hays Parks’s contributions to the study of the law of war were titanic and far-reaching, but perhaps his most notable influence was on the practical study of the means and methods of warfare, particularly with respect to munitions. His work still informs how each of the services conducts legal reviews of weapons. As we have attempted to highlight above, Parks’s work in three areas is a clear model for all law of war practitioners to follow: understanding the science and technology of munitions; practical application of the law; and the necessity for law of war experts to contribute to the practical understanding of the law of war by writing.

Although Parks was never one to brag about himself, a couple of other details of his illustrious career demonstrate why his scholarly works were always grounded in the practical. Parks retired as a Colonel in the U.S. Marine Corps Reserve, but he did so having earned Navy-Marine Corps, Canadian, and British parachutist wings, and even earning his U.S. Army Master Parachutist wings—no small feat. In the U.S. Special Operations Forces (SOF) community, Parks is legendary, and is known to have a distinguished status among our nation’s most elite SOF, particularly at Fort Bragg, North Carolina. He was awarded the U.S. Special Operations Command (USSOCOM) Outstanding Civilian Service Medal in 2001 and the USSOCOM William F. Garrison Award for distinguished legal service to SOF in 2006.

While his career is commendable for the contributions he made to clarifying, applying, and instructing on the law of armed conflict, he may be best appreciated for his dedication to the Soldiers, Sailors, Airmen, and Marines on the ground—the ones who actually engage in combat. That commitment is why Hays Parks continues to be the model of the true warfighter’s lawyer.


COL Joshua F. Berry, U.S. Army, was formerly the Deputy Chief of the National Security Law Division, Office of The Judge Advocate General.  He is currently at student at the National War College.

Michael W. Meier currently serves as the Special Assistant to the Army Judge Advocate General for Law of War Matters. As the senior civilian adviser, he advises on legal and policy issues involving the law of war, reviews proposed new weapons and weapons systems, serves as a member of the DoD Law of War Working Group, and provides assistance on detainee and Enemy Prisoner of War affairs.