The Pelican Brief prompts the characters to explore the differences between morality and legality. What is moral is not always legal, while immorality is not necessarily illegal. The FBI, the CIA, and the police, enforcement organizations meant to uphold the law, do not always act in a moral fashion: FBI head Voyles makes illegal bargains with the President, the CIA operates illegally within American borders, and the police struggle to provide help to Darby even when she is in danger. At the same time, police officer Cleve breaks the law to act in a moral fashion, providing help to Grantham through clandestine means.

The novel’s version of the Supreme Court also illustrates the complex morality of the law. The nine Supreme Court Justices all interpret the law differently, but all believe that they are doing so in a moral fashion—a contradiction that has no obvious answer. Rosenberg, a liberal Justice who dissents loudly and often, believes that he has the most moral position, but he is also in a minority on the Court.

Because morality and legality have so little overlap, Mattiece’s plan to kill two Justices so more amenable ones can be installed in their place is almost successful.