L. Gordon Crovitz has a good piece in today’s Wall Street Journal that navigates the thinking behind the U.S. Supreme Court’s recent decision to reduce the $2.5 billion punitive damage award against Exxon for the Valdez spill nearly 20 years ago and establish some principle to guide future cases. “We should cheer,” Crovitz writes, “when the Supreme Court issues clear, transparent and common-sense rules, giving judges, jurors and citizens new understanding about how the legal system should work.”