Today’s post comes from Sonia Kahn in the National Archives History Office. Visit the National Archives website for a full list of events and activities related to the 100th anniversary of World War I.

On June 15, 1917, just two months after the United States entered World War I, Congress adopted the Espionage Act. The act, which was meant to define the act of espionage during wartime, put new limits to Americans’ First Amendment rights.

The Espionage Act gave the federal government increased leverage to prosecute what it considered unruly elements. Though the charge of espionage included “promot[ing] the success of [the United States’] enemies” it also encompassed a much greater swath of possible violators.

Based on the terms dictated by Congress, anyone who interfered with or attempted to undermine the United States’ war effort could be prosecuted under the law and face a 20-year prison sentence and a $10,000 fine.

Thanks to the convenient wording of the act, those who protested against newly introduced conscription, or against the war itself, became prime subjects for prosecution.

This language allowed the government to target socialists, communists, pacifists, and anarchists—all of which were opposed to the war.

The following year, 1918, Congress passed a harsh companion act to the Espionage Act known as the Sedition Act, which made it a crime to speak ill of or criticize the American government, the Constitution, and remarkably, even the national flag. Although the Sedition Act was repealed three years later, many were charged with sedition during and immediately after World War I, when fear of Communists was rampant.

One notorious example of someone being tried and convicted under the 1917 law was Eugene V. Debs, a prominent socialist and one of the founders of the International Workers of the World.

Debs condemned American involvement in the war from the start, but in 1918 he earned himself a 10-year prison sentence after delivering a speech in Canton, Ohio, in which he strongly criticized the Espionage Act.

Debs appealed his case all the way to the Supreme Court, which ultimately ruled against him. The decision to uphold Debs’s conviction was based on the precedent set by another case, Schenck v. United States, which concluded that speech with the potential to undermine society or the government was not protected under the First Amendment.

Since its passage in 1917, several other prominent people have been charged under the Espionage Act. Julius and Ethel Rosenberg, both New York–born citizens, were tried under the Espionage Act in 1951, ultimately convicted of being Soviet spies, and in 1953 became the first American citizens executed for an espionage conviction.

The Espionage Act is still in effect today. Most notably, in 2013, former National Security Agency contractor Edward Snowden was charged with espionage after he leaked confidential information concerning U.S. Government surveillance programs.

This month will mark the 100th anniversary of the act that for so long, and continues to, define limits of free speech.

The National Archives is commemorating the 100th anniversary of the Espionage Act. It will be on display in the Landmark Documents case in the Rubenstein Gallery from June 15, 2017 through September 13, 2017.