In his speech to Congress during a trip to the US to mark the country’s 250th anniversary, King Charles made repeated references to Magna Carta, the medieval English charter that laid the foundations for the modern rule of law. Dating back to 1215, Magna Carta also established for the first time that the monarch was not above the law. Charles used his speech to reference the common Anglo-American tradition of law, and of how the charter has been cited in more than 160 US judgments of the US Supreme Court. It was notable that the king chose to cite this ancient charter, which stands as a symbol of protecting freedom and guarding against tyranny, at such a tricky moment for US-UK relations. Perhaps not surprisingly in the context of an erratic and controversial US president, the remarks from the king were well received by parts of the audience. In fact, Charles enjoyed a standing ovation when he stated that Magna Carta was the very “foundation of the principal that executive power is subject to checks and balances”. In other words, it serves as the basis for the rule of law. Checks, balances and applause for the king. Charles is only the third ruling British monarch to visit the US. But during all three visits, Magna Carta has been trumpeted in support of a supposedly very special alliance. King George VI, Charles’ grandfather, began this in 1939. Back then, he visited the New York World Fair where Lincoln Cathedral’s original Magna Carta of 1215 was on display as the centrepiece of the British pavilion. Read more: How King Charles charmed the US while taking digs at Trump War broke out that same year, and so Lincoln’s Magna Carta became stranded in the US. It was guarded in the gold depository at Fort Knox, Kentucky, until it could be returned to England in 1946. At a low point in British fortunes following both the fall of France and the Blitz, in the summer of 1941, prime minister Winston Churchill even considered gifting it to the American people. Had he done so, this would have served as a reminder of America’s responsibilities to war-torn Europe.In 1976, when Charles’ mother, Queen Elizabeth II, visited Washington for the bicentenary of American independence, there was again talk – not least from the British prime minister Harold Wilson – of gifting a Magna Carta to the US. In the end, this was resolved by the presentation of a replica crafted in gold and enamel (which is now somewhat sheepishly displayed in the crypt of the US Capitol). Legacy in US statuteIn all of this, Magna Carta for many Americans remains an icon of the rule of law, or what in the US is called “due process”. Where only four of the charter’s original 60 clauses are still operative under English law, the entire text was incorporated in the statute books of no less than 17 US states, beginning with South Carolina in 1836 and ending with North Dakota in 1943.Images of England’s King John presenting Magna Carta to his barons are carved or painted in many state capitols or court houses, including on the vast bronze doors of the Supreme Court building in Washington. The US National Archives (thanks to a long-term loan), and Harvard Law School both possess originals of the English charter. That of the National Archives is via a reissue of 1297, sold to the presidential candidate Ross Perot in 1984, while Harvard’s is from a 1300 reissue, purchased in 1946 as a mere “copy” for US$27.50 (around £7 at the time). This was reauthenticated in 2025 as a lost (and therefore extremely valuable) original. The US issued a commemorative postage stamp in 1965 to mark the 750th anniversary of the sealing of Magna Carta. SUDARSHAN BHATLA/Shutterstock And in the UK, an acre of Runnymede in England, where Magna Carta was sealed, was granted to the American people in perpetuity in 1965. This was done both in honour of a shared respect for the principle of liberty, and as a memorial to President John F. Kennedy, assassinated in 1963. Of course, there are aspects of this story that belong more to the realm of myth than reality. For instance, of Magna Carta’s many appearances in US supreme court judgments, a surprising number cite it not as a touchstone of liberty or the rights of man, but in defence of commercial or corporate privilege. Even so, the standing ovation for King Charles and his remarks about checks and balances suggest that Magna Carta remains a potent symbol. In what was widely received as a pitch-perfect speech, the king reminded the land of the free that the price of US (or indeed UK) freedom is not only eternal vigilance, but a healthy respect for the shared Anglo-American past.Nicholas Vincent does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.