Enforced largely by A. Mitchell Palmer, the United States attorney general under President Woodrow Wilson, the Espionage Act essentially made it a crime for any person to convey information intended to interfere with the U.S. armed forces prosecution of the war effort or to promote the success of the country's enemies. Anyone found guilty of such acts would be subject to a fine of $10,000 and a prison sentence of 20 years.
The Espionage Act was reinforced by the Sedition Act of the following year, which imposed similarly harsh penalties on anyone found guilty of making false statements that interfered with the prosecution of the war; insulting or abusing the U.S. government, the flag, the Constitution or the military; agitating against the production of necessary war materials; or advocating, teaching or defending any of these acts. Both pieces of legislation were aimed at socialists, pacifists and other anti-war activists during World War I and were used to punishing effect in the years immediately following the war, during a period characterized by the fear of communist influence and communist infiltration into American society that became known as the first Red Scare (a second would occur later, during the 1940s and 1950s, associated largely with Senator Joseph McCarthy). Palmer–a former pacifist whose views on civil rights radically changed once he assumed the attorney general's office during the Red Scare–and his right-hand man, J. Edgar Hoover, liberally employed the Espionage and Sedition Acts to persecute left-wing political figures.
One of the most famous activists arrested during this period, labor leader Eugene V. Debs, was sentenced to 10 years in prison for a speech he made in 1918 in Canton, Ohio, criticizing the Espionage Act. Debs appealed the decision, and the case eventually reached the U.S. Supreme Court, where the court upheld his conviction. Though Debs' sentence was commuted in 1921 when the Sedition Act was repealed by Congress, major portions of the Espionage Act remain part of United States law to the present day.