In Steffel v. Thompson et al., the U.S. Supreme Court ruled in favor of a petitioner who was threatened with prosecution for distributing anti-war handbills at a shopping center, but had not yet been prosecuted. The court held that federal courts have jurisdiction to intervene on behalf of individuals facing threats of state criminal prosecution under certain circumstances, even if no state proceedings are underway at the time of the federal suit. This decision clarified and expanded upon previous rulings which stated that federal courts could only intervene once state proceedings had begun or were imminent. The ruling emphasized that an individual does not need to risk arrest before challenging the constitutionality of a law they believe infringes upon their rights.

In the dissenting opinion for Steffel v. Thompson, Justice Rehnquist argued that federal courts should not have jurisdiction over state criminal proceedings unless there is a threat of irreparable injury. He believed that the majority's decision to allow federal court intervention in potential state prosecutions undermined principles of equity, comity, and federalism. According to him, it was inappropriate for a petitioner who had been threatened with prosecution but not yet charged to seek relief in a federal court because no actual controversy existed at this stage. Furthermore, he contended that allowing such actions would encourage individuals facing possible state charges to bypass their local legal systems entirely and go straight to the federal courts instead - an outcome he saw as detrimental both practically and constitutionally.