The U.S. Supreme Court upheld the constitutionality of the federal Fugitive Slave Act of 1793 in Prigg v. Pennsylvania (1842), while striking down a Pennsylvania state “personal liberty” law that conflicted with the Fugitive Slave law. The case involved professional slavecatcher Edward Prigg, who tracked down former slave Margaret Morgan and returned her to her Maryland owner, Margaret Ashmore.

Prigg returned Morgan to Maryland without obtaining the required certificate under federal law because a Pennsylvania state judge refused to issue him one. Pennsylvania authorities then charged Prigg with kidnapping. The two states fast-tracked the litigation and it reached the U.S. Supreme Court.

In his opinion, Justice Story wrote: “Upon these grounds, we are of opinion, that the act of Pennsylvania upon which this indictment is founded, is unconstitutional and void. It purports to punish as a public offence against that state, the very act of seizing and removing a slave, by his master, which the constitution of the United States was designed to justify and uphold.”