A conscientious objector (CO) is an "individual who has claimed the right to refuse to perform military service" on the grounds of freedom of thought, conscience, and/or religion. In general, conscientious objector status is only considered in the context of military conscription and is not applicable to volunteer military forces
The Espionage Act of 1917 prohibited any means to attempt to interfere with military operations or interfere with the military in any way, or support U.S. enemies during the war. The Sedition Act of 1918 extended the Espionage Act to cover more offenses, such as the freedom to express their opinion on the government or war effort in a negative way. With such acts, you were not allowed to support opposing war efforts or speak or do anything about opposing the war.
Unions grew very rapidly during the war but after a series of failed major strikes in steel, meatpacking and other industries, a long decade of decline weakened most unions and membership fell even as employment grew rapidly. Radical unionism virtually collapsed, in large part because of Federal repression during World War I by means of the Espionage Act of 1917 and the Sedition Act of 1918. The major unions supported the third party candidacy of Robert La Follette in 1924.