3Qs: “Poison Pill” hard to swallow, for some

A Delaware Chancery Court ruling last month upheld Airgas, Inc.’s right to employ its share­holders rights plan — a defense known as a “poison pill” — to block an unso­licited offer by Air Prod­ucts. Don Mar­gotta, asso­ciate pro­fessor of finance, dis­cusses the resur­gence of this cor­po­rate defense tactic.