When the Supreme Court hears oral arguments on March 2, 2010 in the landmark gun rights case McDonald v. Chicago, the Second Amendment won't be the only thing on the justices' minds. That's because when it comes to protecting constitutional rights from the depredations of state and local governments, the Court must obey the 14th Amendment, which commands: "No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law."

McDonald will therefore turn on whether the right to keep and bear arms applies to Chicago via the 14th Amendment's Privileges or Immunities Clause or via its Due Process Clause. That distinction matters because the Privileges or Immunities Clause has been a dead letter since the controversial Slaughterhouse Cases of 1873, which gutted the clause while upholding a state-sanctioned slaughterhouse monopoly in Louisiana. And despite overwhelming historical evidence that the Privileges or Immunities Clause was specifically written and ratified after the Civil War in order to secure individual rights against state abuse—including the right to armed self-defense—Slaughterhouse has never been overturned.

So the stakes in McDonald are high indeed. And they aren't just limited to gun rights.

Consider this: Among the legal experts lining up in support of overturning Slaughterhouse and reviving the Privileges or Immunities Clause is liberal law professor Akhil Amar of Yale University. Nobody's idea of a gun nut, Amar is a supporter of progressive politics. And in his opinion, so were the authors of the Privileges or Immunities Clause. "The framers of the 14th Amendment were radical redistributionists," Amar told The Wall Street Journal. "The 13th Amendment frees the slaves and there's no compensation. It's the biggest redistribution of property in history." Under this interpretation, the privileges or immunities of citizenship might include the right to health care, to a living wage, or to some other welfare right fancied by today's progressive activists.

It's a clever argument, but it doesn't hold up. Amar conveniently ignores the 14th Amendment's origins in the free labor philosophy of the Radical Republicans, who drafted and spearheaded its ratification in 1868. Remember that the anti-slavery movement that produced those Republicans rejected human bondage as a violation of natural rights, or as the abolitionist William Lloyd Garrison put it, "man cannot hold property in man." The escaped former slave Frederick Douglass made the same point in the famous letter he wrote to his former master. "You are a man and so am I," Douglass declared, echoing the Lockean idea of possessing a property right to your own body. "In leaving you, I took nothing but what belonged to me, and in no way lessened your means for obtaining an honest living. Your faculties remained yours, and mine became useful to their rightful owner." That's not redistribution, it's restitution. Douglass simply reclaimed his own stolen property from the unjust regime that took it.

In the aftermath of the Civil War, the former Confederate states sought to resurrect that vile regime with a web of laws and regulations that robbed the freed slaves (and their white allies) of their civil, political, and economic rights. Mississippi's Black Code, for example, declared "that no freedman, free Negro, or mulatto…shall keep or carry firearms of any kind," while Louisiana's Black Code mandated that, "Every negro is required to be in the regular service of some white person, or former owner, who shall be held responsible for the conduct of said negro."

That's the historical context that produced the 14th Amendment. As the Institute for Justice writes in the friend of the court brief it filed in McDonald, "To enslave a class of people requires three basic things: destroy their self-sufficiency, prevent them from fighting back, and silence any opposition. Southern states did all of those things both before and after the Civil War, and the point of the Fourteenth Amendment was to make them stop."

In sum, the 14th Amendment was designed to protect an individualistic and market-oriented form of self-ownership, one that includes the right to armed self-defense, the right to private property, the right to liberty of contract, and the right to pursue an honest living free from arbitrary and unnecessary government interference. That's the libertarian promise of the Privileges or Immunities Clause. And that's why Tuesday's arguments in McDonald v. Chicago matter for both gun rights and economic liberty.

Damon W. Root is an associate editor at Reason magazine.