The United States Permanent Paper Law is a rule that says important papers that are printed or published in the U.S. must be made on special paper that will last for a long, long time. The reason for this law is because some papers, like birth certificates or historical documents, need to be kept safe and readable for many years, even hundreds of years.
Think of it like building a really strong and sturdy Lego tower. You don't want your tower to fall apart or crumble down, just like you don't want important papers to fall apart or crumble away over time. The Permanent Paper Law helps make sure that important papers stay strong and readable for a really long time.