President-elect Donald Trump declared on his Twitter - which can perhaps be viewed as a real-time version of the proposed policies of the soon-to-be leader of the free world - his unprompted thoughts on flag burning. He also suggested what should happen to the people who engage in it on Tuesday morning:

Trump's tweet seemingly came out of left field, as he rarely spoke about it on the campaign trail, and it's not a particularly pressing issue. His most high profile utterances on flag burning came over a year ago, in a September 2015 interview with conservative website the Daily Caller, where he made his distaste for it known: “Personally, I don’t think [flag burning] should be legal. Let me ask you a question. It didn’t used to be legal, did it? I see more and more burning of the flag. Did it used to be legal?” He also added, "People burning the flag, I don’t like them in this country."

As to whether it "used to" be legal, that can easily be answered: It's been legal since 1989.

The U.S. Supreme Court ruled in Texas v. Johnson that a flag-burning protestor outside the Republican National Convention in 1984 had been unlawfully arrested, and that the desecration of an American flag is protected by the First Amendment as "symbolic speech." The ruling prompted Congress to pass a Flag Protection Act that same year - which was subsequently found to be unconstitutional by the 1990 case US v. Eichman. Flag burning legality has been settled law ever since.

Beyond that, the Supreme Court has also ruled that "stripping of citizenship" is illegal and unconstitutional. In 1958, Trop v. Dulles made revoking citizenship as punishment (in that case, as retribution for desertion) illegal, while the 1967 decision Afroyim v. Rusk codified that no one with United States citizenship could be involuntarily deprived of it.

What Trump proposed in his tweet is an illegal action punishing a legal action.

Even with flag burning having been legal for nearly three decades, countless politicians have tried to ban it, again, through either new law or a constitutional amendment. The first attempt at such an amendment was in 1989, the same year the Supreme Court legalized it. There have been dozens of such amendments entered into the House of Representatives since then, but few have made it to the Senate, and none made it out. The most recent such attempt, in 2006, died in the Senate, with one vote preventing it from going to the states for ratification. 

Attempts to force such laws into existence are still popular with the voting public, even with multiple decisions against them. Hillary Clinton, who voted against flag burning amendments as a senator, co-sponsored a bill in 2005 that would put flag burning to incite violence on the same legal level as burning a cross. That bill, along with every other proposed flag desecration law since 1990, died on the floor of the Senate.

While Trump's call to unconstitutionally bar flag burning, and unconstitutionally punish those who do it, seemed to come out of nowhere, it might not have after all.

An ABC News reporter noticed that the timing of the tweet lined up perfectly with a story Fox News that was running about a veterans group protesting at Hampshire College in Massachusetts, which had removed all of its flags from campus.

Why did Hampshire College pull its flags down? Because a group of students had allegedly burned one a few days earlier in the aftermath of Trump's election.