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Understanding the Constitution: How States May Respond to Illegal Immigration—Part III

As part of our research into state war powers, my co-author, Andrew T. Hyman, and I examined the scope of “defensive war” as the Founders understood it.
Understanding the Constitution: How States May Respond to Illegal Immigration—Part III
People walk between razor wire and a string of buoys placed on the water along the Rio Grande border with Mexico in Eagle Pass, Texas, on July 16, 2023. Suzanne Cordeiro/AFP/Getty Images
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Commentary
Part I and Part II in this series explained that:
  • the Constitution grants the federal government the exclusive power to wage offensive war, but
  • the states as well as the federal government may wage defensive war;
  • the states may wage defensive war against insurrectionists and against actual or threatened invasions—including invasions by those international criminal gangs the Founders called “enemies of the human race”; and
  • the historical record shows that the mass illegal immigration at the southern border is an “invasion” as the Constitution uses that word.

A Not-So-Hypothetical Situation

As part of our research into state war powers, my co-author, Andrew T. Hyman, and I examined the scope of “defensive war” as the Founders understood it. In other words, we examined what an American state can, and can’t, do when fighting a defensive war.
Rob Natelson
Rob Natelson
Author
Robert G. Natelson, a former constitutional law professor who is senior fellow in constitutional jurisprudence at the Independence Institute in Denver, authored “The Original Constitution” (4th ed., 2025). He is a contributor to The Heritage Foundation’s “Heritage Guide to the Constitution.” He also researched and wrote the scholarly article “Virgil and the Constitution,” whose publication is pending in Regent University Law Review.
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