When Harold Henderson, a 79-year-old retired labor lawyer, was a teenager visiting his grandfather’s farm in Albemarle County, Va., his grandfather showed him a rock. It was a large rock — more like a boulder. While standing on this rock, Henderson’s grandfather said, your great-grandfather was sold as a slave at the age of 12.

Decades later, after poring over census and property records, Henderson’s sisters went looking for the rock. Driving around the area where they expected the rock would be, they instead found a man working at a construction site. The man knew nothing about the history of the land, but he knew about the rock — he had broken it up to make space for a garage and thrown the debris in bushes nearby. Henderson’s sisters went looking in the bushes. The rock, in pieces, was there. Now, a three-pound chunk of it sits in Henderson’s office. To him it’s a symbol and a stark reminder that the justice system in which Henderson built a career — as general counsel for Amtrak and as head of labor relations for the National Football League — is built on a corrupt foundation.

What concerns him is the citation of legal precedents dating to slavery. “It bothers me not so much specifically as a Black person, but as a lawyer,” he said. “The precedent that stands today — there’s still prejudice, bias and misconception that tended to shape the law.”

Justin Simard, a law professor and legal historian at Michigan State University — Henderson’s alma mater — has been fighting bias with an unlikely weapon: footnotes. Director of the Citing Slavery Project, Simard is building a database of cases involving enslaved people and modern cases that cite them as a precedent. He even got the editors of the Bluebook — the legal profession’s arcane but rigorously adhered-to citation bible — to change its rules in its 2021 edition, requiring cases involving slavery to be identified.

Simard got the idea for the rule change when he saw a pre-Civil War case related to slavery cited as precedent in 2012. He started looking for other examples from the past 30 years, thinking he’d find one or two. Instead, he found more than 300.

Simard was disturbed. For a case involving an enslaved person to be good precedent in, say, a property matter, “you have to continue to treat that person as property,” he told me. The new Bluebook citation rule shines a light on this practice, forcing lawyers in search of precedent to find some not entangled with the reprehensible human trafficking that has riven the Western Hemisphere since 1619. Alternatively, these lawyers must own the fact that their legal theories find support in historical suffering.