In an early morning tweet, Donald Trump declared that there “must be consequences” for people who burn the American flag, and proposed they should face a year in prison or even be stripped of their citizenship.

Given Trump’s history of manipulating the news cycle with intentionally provocative tweets, it is difficult to know whether the tweet was a serious sign of his intentions to crack down on political dissent – or simply an attempt to incite left-wing critics and distract from other stories, like the recent coverage of his and his son-in-law’s extraordinary conflicts of interest.

But the tweet combines two deeply unconstitutional ideas long repudiated by the Supreme Court: criminalizing flag burning and stripping Americans of citizenship without their consent.

The Supreme Court struck down Texas’ prohibitions on flag burning in 1989, ruling that flag burning was a protected form of expression under the First Amendment.

Writing for the majority, Justice William Brennan wrote “If there is a bedrock principle underlying the First Amendment, it is that the Government may not prohibit the expression of an idea simply because society finds the idea itself offensive or disagreeable.”

In response, Congress passed a federal law banning flag burning. And the Supreme Court struck it down in 1990.

Despite all this, prohibitions on flag burning have continued to enjoy support among members of both political parties, including former Democratic presidential candidate Hillary Clinton. While a senator in 2005, Clinton co-sponsored a failed bill that would have made flag burning a crime, punishable by up to a year in jail or a $100,000 fine.

The Supreme Court also ruled in 1957 that citizens cannot be stripped of citizenship as punishment for a crime, and in 1967 ruled that citizens cannot be stripped of citizenship at all without their consent.

Again, despite that, expatriation proposals have drawn support from members of both parties.

In 2010, former Connecticut Sen. Joseph Lieberman, who caucused with the Democrats, drafted a failed bill that would have stripped terror suspects of their citizenship — as a means of questioning them without their Miranda rights.

During his presidential run, Sen. Ted Cruz, R-Texas, tried to advance a bill that would strip Americans of their citizenship for the vague offense of providing “assistance” to a terrorist organization. An earlier version of Cruz’s bill in 2014 has a Democrat co-sponsor: Sen. Joe Manchin, D-W.Va.

Trump was possibly reacting to Fox News coverage on Monday of a protest at Hampshire College in Massachusetts earlier this month, where students allegedly burned a flag to protest Trump’s election victory.  Similar campus protests have taken place across the country. On November 9, for example, students at American University in Washington, D.C., burned a flag while carrying signs that said “Stand up to racism,” and “stand against anti-Muslim bigotry.”

Flag burning has a long history in the country as a form of protest, having being used to protest such things as the inauguration of Richard Nixon, and American intervention in Vietnam and El Salvador.

“One of the founding principles of American democracy is that we tolerate all peaceful forms of expression and dissent, said Lee Rowland, a First Amendment attorney with the ACLU. “That includes the right to desecrate and even burn the U.S. flag, as the Supreme Court has also held.”

Rowland added: “Our democracy is strong precisely because we tolerate dissent and peaceful expression of all kinds. The idea that not only would the government criminalize that but actually strip you of your citizenship is so very far from the ideals that are the firmament of our democracy that it’s an appalling suggestion.”

Top photo: Protesters try unsuccessfully to burn an upside down U.S. flag during a protest outside the White House in Washington, D.C.