The history of states pushing back on the federal government is far more interesting than states “trying to keep their slaves” - description of the
Fugitive Slave Act (wikipedia):
The Fugitive Slave Law or Fugitive Slave Act was passed by the United States Congress on September 18, 1850, as part of the Compromise of 1850 between Southern slave-holding interests and Northern Free-Soilers. This was one of the most controversial elements of the 1850 compromise and heightened Northern fears of a “slave power conspiracy”. It required that all escaped slaves were, upon capture, to be returned to their masters and that officials and citizens of free states had to cooperate in this law. Abolitionists nicknamed it the “Bloodhound Law” for the dogs that were used to track down runaway slaves.
Now the good part, those dastardly states trying to excerise power (also from wikipedia):
In 1854, the Wisconsin Supreme Court became the only state high court to declare the Fugitive Slave Act unconstitutional, as a result of a case involving fugitive slave Joshua Glover, and Sherman Booth, who led efforts that thwarted Glover’s recapture. In 1859 in Ableman v. Booth, the U.S. Supreme Court overruled the state court.
In November 1850, the Vermont legislature passed the “Habeas Corpus Law,” requiring Vermont judicial and law enforcement officials to assist captured fugitive slaves. This law rendered the federal Fugitive Slave Act effectively unenforceable in Vermont and caused a storm of controversy nationally. It was considered a “nullification” of federal law, a concept popular in the South among states that wanted to nullify other aspects of federal law, and was part of highly charged debates over slavery. The noted poet and abolitionist, John Greenleaf Whittier, had called for such laws, and the Whittier controversy heightened angry pro-slavery reactions to the Vermont law. Virginia governor John B. Floyd warned that nullification could push the South toward secession, while President Millard Fillmore threatened to use the army to enforce the Fugitive Slave Act in Vermont. No test events took place in Vermont, but the rhetoric of this flare-up echoed South Carolina’s 1832 nullification crisis and Thomas Jefferson’s 1798 Kentucky Resolutions.
I snipped the part about jury nullification, which was just below and, and includes more fascinating history.