Mr Trump's provocative tweets on flag-burning and other topics, including efforts to recount the November 8 presidential vote, came as the Republican worked to fill his Cabinet in advance of his inauguration in January.

The US Supreme Court ruled in 1989 that flag-burning was not a crime but rather a form of protest protected by the First Amendment of the Constitution. The high court has also ruled more than once that citizenship cannot be revoked.

US media outlets, including the New York Times, published articles detailing the court rulings, and some Republicans as well as Democrats took to social media to say Mr Trump was in effect threatening to punish dissent despite constitutional protections.

Mr Trump supporters also took to social media, pointing out that many politicians, including Mr Trump's Democratic presidential rival, Hillary Clinton, had proposed making flag-burning illegal.