For all the commemoration of Antonin Scalia’s sweeping legal theories and biting prose—his promotion of the original 18th-century understanding of the Constitution and his disdain for competing legal philosophies—the justice’s most immediate, powerful, and lasting influence may be felt on one important issue: who can gain access to the courthouse. His opinions on such matters as which parties have “standing” to sue and which types of cases can be tried as class actions tilted the scales of justice sharply toward corporations and away from consumers, environmentalists, and women...