Amid the Trump administration’s threats to deport thousands of immigrant families, state and local governments and community organizations across the country are voicing support for immigrants and refusing to cooperate with federal law. Mayor Lori Lightfoot has declared that Chicago police “will not cooperate with or facilitate any ICE enforcement actions.” The Illinois legislature, supported by Gov. J.B. Pritzker, banned private immigrant detention centers and barred local law enforcement from cooperating with U.S. Immigration and Customs Enforcement.

Their actions echo responses to the Fugitive Slave Act of 1850 and remind us that the structure of government in the United States allows space for resistance to unjust federal policies. In the weeks after Congress passed the law on Sept. 18, 1850, Chicagoans took measures to ensure that it would not be enforced in the city. More than 300 African Americans and white allies gathered in Quinn Chapel, the city’s African Methodist Episcopal (AME) church, to discuss how to protect each other and what next steps to take. Black Chicagoans organized a police force to patrol the streets, looking for would-be slave catchers.

In mid-October that year, a slave catcher from Missouri came to town with an enslaved man as his assistant, distributing handbills that described three people who had escaped from slavery. Several “respectable citizens” of Chicago informed the slave catcher that he was putting his personal safety in danger; he heard he would be tarred and feathered. Meanwhile, his slave boarded a steamer bound for Canada. The slave catcher applied to a Chicago judge for protection, but the judge said there was nothing he could do. Frustrated, the Missouri man left the city.

The next day, the three people he’d been looking for came out of hiding and boarded a boat bound for points east. As a sympathetic news reporter concluded, “Our colored population are fully prepared for any emergency. While they do not propose to commit any violence unless driven to the wall, they will not suffer the new law to be executed upon their persons. In resisting this even to death, they will be sustained by the omnipotent sentiment of the city of Chicago.”