Last week, over a hundred Latino workers mounted a wildcat strike at a UPS facility to protest the actions of a racist supervisor. One of their coworkers, Antoine Dangerfield, took out his phone and began filming the walkout, his excitement growing as he realized what he was witnessing. Dangerfield posted the video online, where it quickly netted millions of views. Shortly after, his employer offered Dangerfield $250 to take the video down. Dangerfield explained to them that that’s not how the internet works, and that he couldn’t remove the video. So, they fired him.

This may seem like a bad reason to fire someone, and Dangerfield’s employer may even admit that it was a bad reason to fire him — but it is still probably legal. That’s because the US, for the most part, follows the at-will rule of employment, where an employee can be terminated for good cause, bad cause, or no cause at all. (Montana is the only state that has some form of just-cause rule.)

Though at-will employment is treated as a fundamental feature of American culture and the economy, the rule is not a creation of Congress or any legislatures; it is wholly judge created. The doctrine first appeared in American law in Horace Gray Wood’s 1871 Treatise on the Law of Master and Servant. By the early twentieth century, the rule had become so common in the courts that the Tennessee Supreme Court expressed it in absolute terms, stating, “All may dismiss their employe[e]s at will, be they many or few, for good cause, for no cause or even for cause morally wrong, without being thereby guilty of legal wrong.”