Haun was a prosecution for violation of an 1818 statute banning the importation of enslaved people to the United States. The defendants sought to have the charge dismissed on the ground that they purchased enslaved people that had been imported illegally but had not participated in the importation itself. The importation clause of the statute, however, was followed by a clause specifically prohibiting the sale or holding of an enslaved person imported in violation of the statute. Justice Campbell noted that the latter clause was preceded by the word “or,” meaning that a violation of one clause and not the other was sufficient for conviction. To prevail on their argument, he explained, the defense would have the court exchange the word “or” for “and,” which Campbell refused to do.

The defendants argued further, however, that congressional power extended to the importation of enslaved people and no further, because Congress lacked the authority to regulate commerce within a state. Campbell rejected this argument as well. By way of analogy, he referred to “extradition laws and treaties requiring the surrender of a fugitive from the justice of foreign nations.” If the United States could order the arrest and removal of a foreign fugitive, he reasoned, it could provide for the removal of others who had entered the country in violation of American law. The suppression of the slave trade, he concluded, was part of the nation’s foreign affairs, over which the federal government had exclusive control.

One of the most notable aspects of the opinion was Campbell’s characterization of the banning of the slave trade in 1808 as “something beyond a regulation of commerce.” The ban, he asserted, had been intended to “withdraw the citizens of the United States from all further violations of human rights which have been so long continued on the unoffending inhabitants of Africa.” Coming from Campbell, who had been a slaveholder before joining the Supreme Court and resigned from the Court at the outbreak of the Civil War, the statement reflected the fact that some slaveholders considered the slave trade immoral (although others opposed it on economic grounds).