In 1877, Hall decided to pursue the study of law. She approached her brother, Ezra, who was already an attorney and Connecticut State Senator, about her decision. Although he gave her no encouragement, upon her insistence, he gave her a copy of difficult legal work. After watching her study the work with great enthusiasm, Ezra decided to allow Hall to apprentice in his office. However, Ezra died a few months later in April 1878. John Hooker, the Clerk of the Supreme Court of Errors, took Hall in as his apprentice, beginning on April 2, 1879. That year, Belva Lockwood became the first woman admitted to argue before the U.S. Supreme Court. Hall studied law and copied and prepared judicial opinions under Hooker's supervision and instruction for over three years.