Publishing false statements knowingly is referred to as libel. This differs from slander which is defamation of character expressed verbally.
Though the US constitution contains an amendment protecting freedom of the press, this amendment does not protect people from false information. The Supreme Court has not allowed people to report false information in particular about individuals that ruin their reputation or defame their character to be protected by the First Amendment.
Plessy v. Ferguson was important because it essentially established the constitutionality of racial segregation. As a controlling legal precedent, it prevented constitutional challenges to racial segregation for more than half a century until it was finally overturned by the U.S. Supreme Court in Brownv.
