The Supreme Court has been quietly revising its decisions years after they were issued, altering the law of the land without public notice. The revisions include truly substantive changes in factual statements and legal reasoning," said Richard J. Lazarus, a law professor at Harvard and the author of a new study examining the phenomenon. The court's secretive editing process has led judges and law professors astray, causing them to rely on passages that were later scrubbed from the official record. The widening public access to online versions of the court's decisions, some of which do not reflect the final wording, has made the longstanding problem more pronounced. Unannounced changes have not reversed decisions outright, but they have withdrawn conclusions on significant points of law. The larger point, said Jeffrey L. Fisher, a law professor at Stanford, is that Supreme Court decisions are parsed by judges and scholars with exceptional care. "In Supreme Court opinions, every word matters," he said. "When they're changing the wording of opinions, they're basically rewriting the law." The court does warn readers that early versions of its decisions, available at the courthouse and on the court's website, are works in progress. A small-print notice says that "this opinion is subject to formal revision before publication," and it asks readers to notify the court of "any typographical or other formal errors." But ... the court almost never notes when a change has been made, much less specifies what it was. And many changes do not seem merely typographical or formal.