A farm boy with a thirst for learning, Bradley managed to find a way to attend Rutgers College. He thereafter passed the New Jersey bar. He grew to be both a reflective master of the law and an active participant in large undertakings; the Camden & Amboy Railroad was his most important client. In 1870 Bradley was appointed to the Supreme Court by President Ulysses S. Grant and was assigned, as a traveling circuit justice, to the Fifth (Southern) Circuit. His first major civil-rights case was United States v. Cruikshank, which he heard initially in federal circuit court in 1874. It concerned an armed attack by whites who killed 60 blacks at a political rally in Louisiana. Bradley ruled that such rights as the citizen's right to vote, to assemble peaceably, and to bear arms and the rights to due process and equal protection were not protected by the federal government but by the states. When the case reached the Supreme Court, the majority held the same view.

In 1883 Bradley and the court majority declared unconstitutional two sections of the Civil Rights Act of 1875, which had forbidden discrimination on the ground of colour in inns, public conveyances, and places of amusement. Bradley held that the act was beyond the power of Congress because the Fourteenth Amendment barred discriminatory actions only by states and not by private individuals. The dissent by Justice John M. Harlan, who called attention to the public nature of inns and restaurants, was later to be followed by Congress in the Civil Rights Act of 1964 and sustained by the Supreme Court under the Commerce Clause, in Heart of Atlanta Motel v. U.S. (1964) and Katzenbach v. McClurg (1964).