John M. Murrin, et al., eds., Liberty Equality Power: A History of the American People, 2nd ed. vol. 1 (Fort Worth: Harcourt Brace, 1999), 455-56.
The Fugitive Slave Act of 1850 gave the federal government more power than any other law passed by Congress. The constitution required that a slave who escaped into a free state must be returned to his or her owner. But it did not specify how that should be done. Under the 1793 Law, Slaveowners could take recaptured property before any state or federal court to prove ownership. This procedure worked well enough so long as states were willing to cooperate. But as the antislavery movement gained momentum in the 1830s, some officials proved uncooperative. And professional slave-catchers went to far kidnapping free blacks, forgoing false affidavits to 'prove' they were slaves, selling them south into bondage. Several northern states responded by passing antikidnapping laws giving alleged fugitives the right to testify on their own behalf and the right to trail by jury. The laws also prescribed criminal penalties for kidnapping. In Prigg v. Pennsylvania's antikidnapping law unconstitutional. But the Court also ruled that enforcement of the Constitution's fugitive slave clause was entirely a federal responsibility, thereby absolving the states of any need to cooperate in enforcing it. Nine northern states thereupon passed personal liberty laws which prohibited the use of state facilities (courts, jails, police or sheriffs and so on) in the recapture of fugitives.