The Supreme Court on Tuesday overturned the conviction of the Arthur Andersen accounting firm for destroying Enron Corp.-related documents before the energy giant’s collapse.

In a unanimous opinion, justices said the former Big Five accounting firm’s June 2002 obstruction of justice conviction, which virtually destroyed Andersen, was improper. The decision said jury instructions at trial were too vague and broad for jurors to determine correctly whether Andersen obstructed justice.