Complex sentence: The defendants had been indicted under the National Prohibition Act and were appealing their conviction, arguing that the eighteenth Amendment had not been properly ratified, as the Congress of the United States had chosen it be ratified by state legislatures instead of constitutional conventions.
Split into simpler sentences: The defendants had been indicted under the National Prohibition Act and were attempting to quash their indictments, arguing that the Eighteenth Amendment had not been properly ratified. Their reasoning was that the Congress of the United States had chosen to ratify it by usage of state legislatures instead of constitutional conventions.