A major cause of dissension between the Southern slaveholding, and Northern free states was the lack of assistance given by northerners to southern slave-owners and their agents seeking to recapture escaped slaves. See Underground railroad. In 1842 the Supreme Court had ruled that states did not have to proffer aid in the hunting or recapture of slaves, and in some areas locals had actively fought attempts to seize black fugitives and return them to the South. Some northern states passed personal-liberty laws mandating a jury trial before alleged slaves could be moved, others forbade the use of local jails or the assistance of state officials in the process of arrest or return.
In response, the Fugitive Slave Bill of 1850 made any federal marshal or other official who did not arrest an alleged runaway slave liable to a fine of $1,000. Law enforcement officials everywhere in the United States now had a duty to arrest anyone suspected of being a runaway slave on no more evidence than a claimant's sworn testimony of ownership. The suspected slave could not ask for a jury trial or testify on his or her own behalf. In addition, any person aiding a runaway slave by providing food or shelter was to be subject to six months' imprisonment and a $1,000 fine. Officers capturing a fugitive slave were entitled to a fee for their work.
In fact the Fugitive Slave Law brought the issue home to anti-slavery citizens in the North, since it made them and their institutions responsible for enforcing slavery. Even moderate abolitionists were now faced with the immediate choice of defying what they believed an unjust law or breaking with their own conscience and belief.