President-elect Donald Trump’s recent tweet about flag burning has re-ignited a free speech debate.

The issue of flag burning has been taken up by the Supreme Court not once but twice - and in both cases, flag burning was ruled protected free speech under the First Amendment.

Flag burning is legal in the United States because of the 1989 case "Texas v. Johnson." The Supreme Court ruled 5-4 that flag burning was a form of "symbolic speech" and protected by the first amendment.

The ruling came after an appeal from Lee Johnson. He had been convicted and sentenced to one year in prison for burning a flag during a protest at the Republican National Convention in the 1980s.

"It's taking a national symbol and attaching one permissible meaning to it,” Johnson said.

The nation's highest court ruled that the Texas law banning flag burning was unconstitutional. A year later, the court again affirmed its decision when it ruled the "Flag Protection Act of 1989" was unconstitutional - that was a law passed by Congress in response to the Johnson decision.

"It protects a person's right to burn the flag, even though we don't like it, but it also protects everyone else’s right to criticize that,” Brad Kizzia, a constitutional lawyer, said.

Even though flag burning may be a form of free speech - it doesn't necessarily grant protesters protection from arrest in all situations.

Outside this year's Republican National Convention in Cincinnati, 16 protesters - including Johnson - were arrested after burning a flag. The protesters were charged with inciting a crowd that ultimately turned aggressive.

The takeaway here is like any freedom, there are limitations to speech.