While riding circuit, Justice Bradley heard a case identical to three others heard in the Supreme Court of Louisiana, the latter of which went to the Supreme Court of the United States as the Slaughterhouse Cases. An association of butchers sought to enjoin the enforcement of a state law granting a monopoly to one company for the operation of slaughterhouses in New Orleans. The plaintiffs argued that the monopoly violated the Fourteenth Amendment by depriving them of privileges and immunities of United States citizenship.

Bradley, along with U.S. Circuit Judge William B. Woods (later a Supreme Court justice), ruled for the plaintiffs. “[W]e may safely say,” wrote Bradley, “it is one of the privileges of every American citizen to adopt and follow such lawful industrious pursuit—not injurious to the community—as he may see fit, without unreasonable regulation or molestation, and without being restricted by any of those unjust, oppressive, and odious monopolies or exclusive privileges which have been condemned by all free governments.” Looking at the Louisiana statute, which forced a butcher to use only the slaughterhouse facilities of one privileged company, Bradley found it “difficult to conceive of a more flagrant case of violation of the fundamental rights of labor.”

In the similar cases before it, the Louisiana Supreme Court disagreed with Bradley, finding the monopoly to be valid. In 1873, the Supreme Court affirmed that judgment by a vote of 5–4, with Bradley in dissent. The Court interpreted the Privileges or Immunities Clause of the Fourteenth Amendment far more narrowly than Bradley had, holding that it applied only to a small set of rights pertaining to national citizenship and that the vast majority of rights could be protected by the states alone. The landmark decision had far-reaching consequences, placing severe limits on the scope of federal enforcement of black civil rights.