In Epperson et al. v. Arkansas, the U.S. Supreme Court ruled that an Arkansas statute prohibiting the teaching of evolution in public schools violated the First Amendment's Establishment Clause, which prohibits government from making any law "respecting an establishment of religion." The court found that by banning the teaching of a scientific theory because it conflicced with biblical interpretations, Arkansas was effectively endorsing a particular religious viewpoint and thus violating constitutional principles separating church and state. The case arose when Susan Epperson, a high school biology teacher, challenged this law as unconstitutional after she was threatened with dismissal for planning to teach about evolution in her class. In its unanimous decision favoring Epperson, the court emphasized that while states have power over their educational systems they cannot use this authority to infringe upon constitutionally protected rights or freedoms.

In the dissenting opinion for Epperson et al. v. Arkansas, Justice Black argued that the majority's decision was an overreach of judicial power and a violation of states' rights to control their own educational systems. He contended that it is not within the Court's jurisdiction to decide what should or shouldn't be taught in schools, as this responsibility lies with local school boards and state legislatures who are more familiar with their communities' needs and values. Furthermore, he expressed concern about setting a precedent where courts could dictate curriculum content based on personal beliefs about scientific truth or religious neutrality rather than constitutional law. Instead, he suggested that if parents disagree with certain teachings they can voice their concerns through democratic processes such as voting or petitioning lawmakers.