President Biden faces many well-publicized deadlines. But there’s one that has flown under most everyone’s radar. Biden has less than a month to make a decision about still-withheld records on one of the most consequential murders of the 20th century. Nearly 30 years ago, Congress unanimously passed the President John F. Kennedy Assassination Records Collection Act, a landmark moment in the fight against government secrecy. In the ensuing years, many documents were handed over to the National Archives, surprising and thrilling skeptics of big government. But the euphoria soon died down. Some of the more sensitive documents were either produced...