Yes, it was required by the US Constitution. But, Northern States and Northern Abolitionists tried hard to circumvent this requirement or change the laws. Also many broke the law and helped slaves escape to Canada.

Before the Revolution, in 1772, Lord Chief Justice Mansfield ruled in the “Somersett Case”, that slavery was not a natural condition, that it was not found in English common law and that it was so odious that “nothing can be found to support it but positive law.”

As there was no positive law in England allowing slavery, the Justice ruled that Somersett, who was a Virginia slave, brought to England by his master, was free.

This judgment, of course, became part of the case law of the British North American colonies. It alarmed the slave states but they had “positive laws” allowing slavery in place. After or during the revolution, most of the Northern states abolished slavery (some immediately, some gradually).

The Southern slave states were worried that Northern states would apply the Somersett precedent to escaped slaves, and declare them free upon entering their borders. Therefore, they inserted the “Fugitive Slave Clause” in the US Constitution. (Article 4, Section 2). This clause was given enforcement mechanisms by the “Fugitive Slave Act” of 1793.

The first abolitionists in America operated within the law to promote Abolition:

• They operated to pass abolition laws or constitutional clauses in State legislatures and constitutional conventions from 1777 to 1804. These succeeded in abolishing slavery (sometimes gradually) in all the “non–slave States” and were attempted but failed in some of the Slave states (Virginia in 1785, for example).

• They succeeded in limiting the spread of slavery to the Northwest Territories in the Northwest Ordinance of 1787.

• They succeeded in banning the importation of slaves to the USA in 1807.

• They then worked to find legal methods to undermine the Fugitive Slave Act of 1793.

o They ruled (successfully) that voluntary transportation of slaves into free states automatically made slaves free (as per Somersett) and that the Fugitive Slave Act only applied to slaves who escaped to free states.

o They passed “personal liberty laws” which forbade the use of State resources to enforce the Fugitive slave act, and other laws which made the fugitive slave act more difficult to enforce.

o The US Supreme Court ruled (in Prigg v. Pennsylvania - 1842) that these State laws refusing State support to the enforcement of the Fugitive Slave Act were constitutional.

This led to the passage of the “Fugitive Slave Act of 1850”, by the US Congress, which fined officials who did not arrest fugitive slaves and citizens who aided them.

It was really only after the Fugitive Slave Act of 1850, that some Abolitionists began to consider acting against the authority of law. There was still recourse to legal measures:

• In 1854, the Wisconsin Supreme Court ruled the Fugitive Slave Act unconstitutional (over-ruled by the US Supreme Court in 1859).

• Vermont passed the “Habeus Corpus Law” which required the State to “protect and defend any person in Vermont arrested or claimed as a fugitive slave”. This made enforcement of the Fugitive Slave Act almost impossible, which led to President Millard Fillmore contemplating the use of military force against Vermont to enforce it. He did not, and essentially the Fugitive Slave Act was never (or rarely, there are 4 cases) applied in New England.

At this point, the Abolitionists were still using the legal framework, but their legal arguments were becoming more dubious and their laws more controversial and contentious. Also, some abolitionists became prepared to act against the authority of the law.

• A pastor in Syracuse New York wrote in 1855 that he had helped 30 slaves escape to Canada in the last month, and that if authorities wanted to arrest him, they could throw him into jail, but that he was confident that his friends and supporters would level the jail and free him.

• Several years earlier, abolitionists had freed by force a captured fugitive slave in Syracuse. (the “Jerry Rescue”)

• In a somewhat comical instance, a free black servant in Pittsburg was “rescued” and spirited away by abolitionist black waiters in a hotel dining room, before his protests that he was already a free man were heard.

Despite a few acts of civil disobedience, in the main, the abolition movement still mostly supported legal or electoral methods to oppose slavery.

Many, however, participated in the “Underground Railway”, which worked to circumvent the Fugitive Slave laws by secretively transporting escaped slaves to Canada.