This is a unique look at race relations in the North in the late antebellum era. It displays both discrete and blatant attempts to help fugitive enslaved people, regardless of the federal and local laws at the time.
At that time, the federal government had the Compromise of 1850 on the books, which made it clear that fugitives would be returned to their owners, and federal officers could draw citizens into apprehension and restraint of those who had run away. That put US Marshals in the Northern states in an awkward position if they were to enforce that legal structure of the Compromise in good faith.
But marshals were political appointees drawn from local populations so that they would have a feel for local sensitivities in delicate situations. So, many local laws were legislated to protect local law enforcement officers and, in some cases, citizens from being drawn into those murky waters. In most Northern states, in the last half of the decade of the fifties, very few prosecutions resulted in the transfer of a fugitive to the South, and it became a matter of debate in Congress.