Editor’s Note: On Friday, Sept. 29, “Third Rail with OZY” will discuss freedom of speech in the United States.

These stories from The Conversation archive explore what speech is protected, what isn’t – and the gray areas in between.

1. On the field

President Donald Trump recently tweeted that athletes who “take a knee” during the national anthem to protest police brutality should be fired. In response, some sports team owners have knelt alongside their players in solidarity. Others have criticized the president with statements like “Our country needs unifying leadership right now, not more divisiveness.”

Elizabeth Tippett, law professor at the University of Oregon, writes that the idea that corporate political speech should be protected under the First Amendment is what underpins the decision to allow corporations to fund political ads in Citizens United – a Supreme Court decision that has been vehemently opposed by liberals.

She writes, “The kind of statements we’ve heard from NFL and NBA team owners offers a counterpoint to the kind of corporate speech most feared by commentators following Citizens United – that of faceless corporations pouring money into elections in service of their ‘greedy ends.’”

2. On campus

What about speech on university campuses?

After a speech by Milo Yiannopolis was canceled by UC Berkeley earlier this year, UC Irvine professors Erwin Chemerinsky and Howard Gillman argued that administrators must do everything to protect free speech, until it becomes an unmanageable threat to public safety – and that the event at Berkeley met that standard.

They write: “If there is blame to be assigned, it should focus on the small number of outsiders who were intent on using violent and unlawful means to disrupt the event.”

3. & 4. Online

In 2003, the Supreme Court ruled that there was no First Amendment protection for cross burning, which is meant only to intimidate or threaten violence. “But what constitutes a burning cross in the digital era?” asks Jessie Daniels, a digital sociologist at City University of New York.

She has examined the spread of websites dedicated to white supremacy, including one called Stormfront. She writes, “Since 2009, there have been nearly 100 homicides attributable to registered members of the site, prompting the Southern Poverty Law Center to call it ‘the murder capital of the internet.’” Preventing violence that arises from abuse of free speech will require us to think more critically about the dangers of online speech, she argues.

On the other hand, the dangers of censorship can also have serious implications. Consider the way President Trump has blocked some Twitter followers on his personal @realDonaldTrump account. A lawsuit has been filed arguing that because it is the president’s account it constitutes a public forum and is protected by the First Amendment, explains Clay Calvert, a mass communications scholar at the University of Florida.

Calvert writes: “When people complain to Trump on his Twitter account about his policies, they not only are engaging in free speech, but also are petitioning the government.” How the case turns out could be a major breakthrough for how we apply the First Amendment in the digital age.

5. On the page

Libraries across the country celebrate Banned Book Week, dedicated to raising awareness about the dangers of censoring printed works. In 2012, one librarian decided to raise awareness by actually banning a book and seeing how the community would react. While there was significant outcry on social media, librarian Scott DiMarco of Mansfield University of Pennsylvania writes, few took concrete actions to remove the ban – a reminder to be vigilant and ask ourselves if we’re willing to do what it takes to defend our First Amendment rights.