When the line between police and military blurs, you get the Stephon Clark tragedy The military is trained to use violence to proactively destroy their enemies. We don't need that mindset in our domestic peacekeepers.

Christopher J. Coyne and Abigail R. Hall | Opinion contributor

Show Caption Hide Caption Al Sharpton attacks Trump at funeral for Stephon Clark Sharpton gave the eulogy for Clark, 22, to the overflowing Bayside of South Sacramento Church as he held tightly to Stephon's distraught brother, Stevante, who frequently grabbed the microphone.

Three years ago this week, Walter Scott set out to fix a broken tail light in Charleston, S.C. Before he could do that, he was stopped by police officer Michael Slager. After an altercation including a brief struggle over the officer's Taser, Walter ran. Within 15 steps he had eight bullets in his back, ending his life just two months after his 50th birthday. Video of the incident showed that he was no immediate threat to the officer who shot him.

The recent and tragic death of 22-year-old Stephon Clark in Sacramento also raises serious concerns about aggressive police tactics. The shooting has sparked widespread protests in both Los Angeles and New York and is only the most recent example of an overly zealous, police force in which two officers responding to a report of someone breaking car windows utilized a helicopter — and 20 bullets.

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This tragic event provides an opportunity to revisit the nation-wide debate over the militarization of police with Sacramento serving as a microcosm of broader issues. According to a 2014 report on a Department of Defense program called the 1033 Program, which was established in the 1990s, the Sacramento police force possessed more than 1,000 assault rifles, 14 helicopters, eight grenade launchers and an airplane.

How is it that police have come to use such aggressive tactics? How is it that something like a simple vandalism investigation ends in the death of a young man, clutching his cell phone, in his grandmother's backyard?

While many factors converged to create the current atmosphere sounding policing, there is one cause that is often overlooked: How America’s foreign policy helped create some of the very domestic controversies, such as militarization of the police, of the last few years.

There’s more to it than you might think. At least part of the answer lies in the U.S. government’s proactive foreign policy, which involves using military force to intervene around the globe.

The Founding Fathers recognized that the police and military serve very different functions. Police are domestic peacekeepers. They uphold the law and protect the rights of citizens — both offenders and victims alike. They are to use violence only as a last resort.

The military, by contrast, is tasked with fighting enemies of the U.S. in foreign conflicts. They are trained to use violence to proactively destroy their enemies and advance the interests of the U.S. government abroad.

When the U.S. government deploys the military abroad, it provides an opportunity for those involved in foreign interventions to experiment with new methods, tactics and the equipment. These military innovations are often imported back and used domestically, within the United States, including in domestic policing activities. When this happens the distinction between the traditional peacekeeping function of police and the more aggressive approach of the military begins to blur.

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Take, for example, the development of the first Special Weapons and Tactics Teams (SWAT) in the United States. Former LAPD officer John Nelson first suggested the idea in the mid-1960s. Nelson, a former Marine, had been part of an elite Force Recon unit in Vietnam. These units were highly trained at gathering intelligence and engaging enemy forces deep behind enemy lines. They killed far more adversaries than their regular Marine counterparts and were known for being particularly aggressive.

Upon returning from Vietnam, Nelson suggested implementing a Force Recon-style team within the LAPD to respond to and better control groups during race riots. His superiors embraced the idea, and the first SWAT team was formed. The unit continued to incorporate new military techniques from Vietnam, including guerilla warfare techniques. The SWAT team became a permanent fixture in 1971.

As the U.S. government began to focus on issues with substantial domestic implications beyond day-to-day law enforcement—particularly drugs and terrorism—the use of SWAT teams and other military tactics expanded dramatically. Regular police, now on the “front lines” of these domestic policy “wars,” now followed their SWAT brethren in incorporating additional military tactics and tools into their day-to-day operations.

Beginning in 1990, for example, the Department of Defense began a program to transfer military equipment such as armored vehicles, riot gear, surveillance equipment, and weapons to state and local law enforcement agencies for the purposes of fighting the war on drugs. By 2011, with local police involved in not only drug enforcement but counterterrorism efforts, some $500 million in military weapons, gear, and supplies moved from the military to law enforcement.

And SWAT teams? Their use has exploded. By 2000, some 90% of police departments serving populations of 50,000 or more had a SWAT team. Current estimates place the number of domestic SWAT no-knock raids as high as 20,000 annually.

Given the continued influx of military equipment and integration of military training and tactics into local law enforcement operations, it should come as no surprise that some members of police forces have come to act like an occupying military force as opposed to peacekeepers. From the weapons in their employ, to dressing in “battle dress uniform” or BDUs, to the organizational structure of their units, the link between the military and the domestic police is clearer than ever and shows no signs of slowing down.

It’s in every law-abiding citizen’s best interest for our police to be well-protected and able to perform their jobs effectively. The anniversary of Walter Scott’s death offers the opportunity to continue the discussion over whether that should include militarization.

Christopher Coyne, an associate professor of economics at George Mason University Abigail Hall, an assistant professor of economics at the University of Tampa, and, are coauthors of the new book Tyranny Comes Home: The Domestic Fate of U.S. Militarism, published by Stanford University Press.