Many provisions of the nation’s founding ch As the nation approaches its 250th birthday next year, the National Archives has mounted its first display of the entire Constitution.The exhibition gives viewers a chance to see not only the original Constitution when it was ratified but also the amendments that have revised it over time, notably by guaranteeing Black men and then all women the right to vote. Presidents have often pushed the scope of their power under the Constitution, but President Trump has been unusually assertive. Here’s a look at some of the provisions that have figured in his first term and in the early months after his return to office.The Bill of Rights often gets more attention than the original Constitution. But as Justice Antonin Scalia used to point out, the rights detailed in the first 10 amendments would be mere “parchment guarantees” without what preceded them. “The real key to the distinctiveness of America,” he said, “is the structure of our government.”First Amendment The First Amendment protects, among other things, freedom of speech and of the press. The Trump administration has been accused of testing its limits by threatening critics with prosecution for hate speech and suggesting that disfavored commentary could be subject to regulatory actions.Second Amendment The Second Amendment has two clauses, and scholars differ about how they interact. The first concerns “a well-regulated militia,” the second “the right of the people to keep and bear arms.” In decisions Mr. Trump has strongly endorsed, the Supreme Court has ruled that the amendment protects an individual right, not tied to militia service, for law-abiding people to keep guns for self-defense. The main part of the Constitution spans four pages and mostly concerns the structure of the government. Tellingly, Congress comes first, in Article I, followed by the presidency in Article II and the judiciary in Article III.Article I, Section 3 Impeachments of presidents are rare. There have been four in the history of the Republic, two of them of Mr. Trump. (The others were of Andrew Johnson in 1868 and Bill Clinton in 1998.) The number of convictions, which require a two-thirds majority of the Senate: zero.Article I, Section 9 The Constitution’s foreign emoluments clause bars many government officials from accepting gifts from “any king, prince or foreign state” without the consent of Congress. It prompted lawsuits that were dismissed as moot after Mr. Trump’s first term. His acceptance of a jet worth hundreds of millions from the government of Qatar this year raised additional questions. Later amendments addressed gaps and shortcomings in the original document. The most important were the three ratified after the Civil War: to outlaw slavery, to insist on equal protection under the law and to guard the right to vote.14th Amendment, Section 1 The 14th Amendment, adopted in 1868, says that “all persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States.” Mr. Trump says the provision does not guarantee birthright citizenship to those born to parents who are in the country unlawfully or temporarily.14th Amendment, Section 3 The provision bars those who had taken an oath to support the Constitution from holding office if they then engage in insurrection. The Supreme Court ruled that Colorado could not use it to take Mr. Trump off the ballot.22nd Amendment, Section 1 Later amendments were printed rather than handwritten. The 22nd Amendment codified a tradition dating back to George Washington that presidents should serve no more than two terms. It was adopted in 1951, after Franklin D. Roosevelt broke with that tradition, winning election four times. Mr. Trump has suggested that he might try to serve a third term.25th Amendment, Section 4 The 25th Amendment sets out an elaborate method of removing a president “unable to discharge the powers and duties of his office.” After the Jan. 6 attack, the House called on Vice President Mike Pence to invoke the amendment to remove Mr. Trump. He refused, saying the amendment concerned presidential incapacity and was not “a means of punishment or usurpation.”The U.S. Constitution is the oldest written national constitution still in force anywhere in the world. Its durability, its relative brevity and its central place in the American experience invite and reward reading and reflection.