Fugitive state law required northern in returning what

In response to the weakening of the original fugitive slave act, the Fugitive Slave Law of 1850 penalized officials who did not arrest an alleged runaway slave, and made them liable to a fine of $1,000 (about $29,000 in present-day value). Law-enforcement officials everywhere were required to arrest people suspected of being a runaway slave on as little as 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.[6]In addition, any person aiding a runaway slave by providing food or shelter was subject to six months' imprisonment and a $1,000 fine. Officers who captured a fugitive slave were entitled to a bonus or promotion for their work.

(RUN AWAY SLAVES is the answer)