The Espionage Act made it a crime to help wartime enemies of the United States, but the Sedition Act made it a crime to express an opinion that contradicted that of the government.
Socialist Eugene V. Debs was sentenced to 10 years in prison under this law.
Both the Espionage Act and the Sedition Act were repealed in 1921.
Text of the Sedition Act
Whoever, when the United States is at war, shall willfully make or convey false reports or false statements with intent to interfere with the operation or success of the military or naval forces of the United States, or to promote the success of its enemies, or shall willfully make or convey false reports or false statements, or say or do anything except by way of bona fide and not disloyal advice to an investor or investors, with intent to obstruct the sale by the United States of bonds or other securities of the United States or the making of loans by or to the United States, and whoever when the United States is at war, shall willfully cause or attempt to cause, or incite or attempt to incite, insubordination, disloyalty, mutiny, or refusal of duty, in the military or naval forces of the United States, or shall willfully obstruct or attempt to obstruct the recruiting or enlistment services of the United States, and whoever, when the United States is at war, shall willfully utter, print, write or publish any disloyal, profane, scurrilous, or abusive language about the form of government of the United States or the Constitution of the United States, or the military or naval forces of the United States, or the flag of the United States, or the uniform of the Army or Navy of the United States into contempt, scorn, contumely, or disrepute, or shall willfully utter, print, write, or publish any language intended to incite, provoke, or encourage resistance to the United States, or to promote the cause of its enemies, or shall willfully display the flag of any foreign enemy, or shall willfully by utterance, writing, printing, publication, or language spoken, urge, incite, or advocate any curtailment of production in this country of any thing or things, product or products, necessary or essential to the prosecution of the war in which the United States may be engaged, with intent by such curtailment to cripple or hinder the United States in the prosecution of war, and whoever shall willfully advocate, teach, defend, or suggest the doing of any of the acts or things in this section enumerated, and whoever shall by word or act support or favor the cause of any country with which the United States is at war or by word or act oppose the cause of the United States therein, shall be punished by a fine of not more than $10,000 or the imprisonment for not more than twenty years, or both: Provided, That any employee or official of the United States Government who commits any disloyal act or utters any unpatriotic or disloyal language, or who, in an abusive and violent manner criticizes the Army or Navy or the flag of the United States shall be at once dismissed from the service...
When the United States is at war, the Postmaster General may, upon evidence satisfactory to him that any person or concern is using the mails in violation of any of the provisions of this Act, instruct the postmaster at any post office at which mail is received addressed to such person or concern to return to the postmaster at the office at which they were originally mailed all letters or other matter so addressed, with the words "Mail to this address undeliverable under Espionage Act" plainly written or stamped upon the outside thereof, and all such letters or other matter so returned to such postmasters shall be by them returned to the senders thereof under such regulations as the Postmaster General may prescribe.