The law compelled people of all States to “assist” Federal marshals and their deputies with the apprehension of suspected runaway slaves. It brought all trials involving alleged fugitive slaves under Federal jurisdiction. It included large fines for anyone who aided a slave in his escape, even by simply giving him food or shelter.
On top of it, bounties were paid to commissioners in fugitive slave cases: $10 if a person was sent back to slavery and $5 if the person was allowed freedom. The Federal government was paying people to capture other people and send them to slavery.
The act also suspended habeas corpus and the right to a trial by jury for alleged “slaves,” and made their testimony inadmissible in court. On the other hand, the written testimony of the supposed slave master, which could be presented to the court by slave hunters, was given preferential treatment.