In Kaplan v. California, the U.S. Supreme Court upheld a conviction for distributing obscene material, ruling that states have the right to regulate obscenity and do not need to rely on expert testimony in determining whether or not something is obscene. The case involved Marvin Miller who was convicted under California law for mailing brochures advertising adult books with explicit sexual content. He argued that his First Amendment rights were violated and appealed his conviction up to the Supreme Court after losing in lower courts. The court ruled 5-4 against him, stating that while abstract discussions of sex are protected by free speech laws, depictions designed purely for their erotic effect fall into a category of "obscene" material which can be regulated by state law without violating constitutional protections on free speech. Furthermore, they held that it's within the purview of judges and juries - rather than experts - to determine what constitutes obscenity based on average person standards.

In the dissenting opinion for Kaplan v. California, Justice William O. Douglas argued that obscenity should not be a punishable offense under the First Amendment's protection of free speech and expression unless it incites violence or is harmful to children. He believed that adults should have full access to materials they wish to consume without government interference, as long as these materials do not harm others or society at large. Furthermore, he criticized the majority's reliance on community standards in determining what constitutes obscenity because such standards are subjective and can vary widely from one community to another. This could lead to inconsistent application of laws across different jurisdictions and potentially infringe upon individuals' constitutional rights.