This summer featured at least a dozen stories of black Americans across the country having the police called on them for little or no reason at all.

Famously, two black men in Philadelphia were arrested while simply waiting for a friend at a Starbucks.

Then the police were called on a black family grilling at a park in California. They were called again on a black child mowing a lawn in Ohio. And again on a black Yale University student napping in a common room. And again on a black Wisconsin man unlocking his own car.

It’s bad enough that a few white Americans are bringing in the law over mundane and ordinary behavior. But more dangerously, others are appointing themselves officers of the law.

In Clearwater, Florida, a man named Michael Drejka deputized himself to handle a traffic infraction he believed to have been committed by Markeis McGlockton, a black man.

For the alleged crime of parking in a handicapped spot, Drejka fatally shot McGlockton in the chest in front of his young children and girlfriend. Pinellas County law enforcement argued that Florida’s “stand your ground” law rendered his actions self-defense and, therefore, legally permissible.

Drejka, it turned out, had a history of punishing perceived traffic violations with threats of violence — and, at least on one occasion, of hurling racial insults. Only after weeks of outrage did prosecutors charge him with manslaughter.

There’s a direct line between what happened to those people who had the police called on them and Markeis McGlockton. Beyond the obvious racist underpinnings of these incidents lurks something far more sinister: the rise of racially motivated vigilantism.

Instead of allowing the police to perform their jobs, some white Americans have taken the responsibility of investigating crimes and pursuing criminals upon themselves.

Take the example of the white man in North Carolina, who demanded to see the pool passes of a black mother and her son in a video that went viral. It was as if he’d been personally charged with safeguarding the private pool there.

“Concerned citizens” like these aren’t even stopping actual crimes. Instead, they’re attempting to prosecute completely imagined crimes — acts made criminal merely by the presence of a black person.

Consider the now-infamous Alison Ettel, dubbed “Permit Patty,” who called the police on Jordan Rogers, an eight-year-old black girl, for selling water without a permit. Did Ettel even know if a permit was necessary?

It’s one thing to point out that these incidents show bias. But the more pressing question is this: What keeps empowering white Americans to act on these biases?

There’s a hint in the Drejka case.

Whereas Alison Ettel acted as judge and jury, Michael Drejka acted as judge, jury, and executioner — taking a man’s life for what Drejka, not the criminal justice system, determined to be a crime. The promise of impunity offered by “stand your ground” laws ensures that others will feel similarly empowered.

There’s good reason to feel empowered: Under many state statutes, police officers only need to claim that they feared for their lives to justify shooting unarmed suspects. So it stands to reason that ordinary citizens can invoke “stand your ground” laws to do the same.

“Stand your ground” laws create a slippery slope in at least 25 states across the country. At their worst, they allow racial bias to manifest as legally permissible murder.

As Americans debate how to combat racially motivated 911 calls — including imposing a criminal penalty for them, as one New York bill would do — it’s worth considering the deadly consequences of what happens when citizens act on vigilante impulses.