President-elect Donald Trump suggested Tuesday that burning the American flag should be criminalized.

"Nobody should be allowed to burn the American flag -- if they do, there must be consequences -- perhaps loss of citizenship or year in jail!" Trump wrote in an early morning Twitter post.

The protest was confirmed to be constitutional following a landmark 1990 Supreme Court case. The top court ruled then that a federal law against desecration of the flag violated the First Amendment of the Constitution, which guarantees freedom of speech.

And in a separate 1967 case the Supreme Court ruled that American citizens cannot be stripped of their citizenship involuntarily.

Trump did not specify what prompted his call.

Speaking to CNN, Trump transition spokesman Jason Miller insisted that "flag burning should be illegal.

"The president-elect is a very strong supporter of the First Amendment, but there's a big difference between that and burning the American flag," he said.

It is not clear how those two seemingly at odds sentiments could be reconciled, and when repeatedly questioned about constitutional law, the spokesman would only say "flag burning should be illegal. End of story".

At the White House, spokesman Josh Earnest insisted that while some may find the practice objectionable, "we have a responsibility as a country to carefully protect our rights that are enshrined in the constitution".

He added that free speech should be protected "not just when we agree with it but also when we find it offensive".