The Fugitive Slave Act of 1850 was an extremely controversial law that deepened the divisions in the country over the issue of slavery. The law was part of a compromise between free and slave states that prevented the secession of states where slavery was legal. The compromise ultimately failed when the Civil War broke out 10 years later.
The Fugitive Slave Act required U.S. citizens to assist in the return of escaped slaves. This applied whether the citizen was a resident of a slave state or a free state. Many white residents of free states were outraged by this demand. They were appalled that they were required to assist in the return of slaves to their masters. The law's requirements led many of those in free states to become even more antagonistic to slavery then they had been before the law was passed.
Another section of the law that upset many white citizens of free states was the establishment of a separate legal procure to deal with those accused of being fugitive slaves. Accused fugitives were not tried in the regular courts, but had their fates decide by special commissioners. A large number of people in free states felt that this process was a violation of a person's basic legal rights.