He returned to Indianapolis, where he became head of one of the state's leading law firms; his most famous partner was future United States President Benjamin Harrison. He took on several high-profile cases, including the Ex parte Milligan case, which ended before the United States Supreme Court, who ruled that Lambdin P. Milligan, who had been arrested during the war for subversive activities, and tried and convicted by a military tribunal, should be released as the tribunal had no authority to prosecute so long as the civil courts were still in operation.