THE TRIGGER: Shares of Constellation Brands fell after the Justice Department sued to block Anheuser-Busch InBev's proposed purchase of Mexican brewer Grupo Modelo, which the government said could lead to higher beer prices for Americans.

THE BACKGROUND: It hurts Constellation's related $1.85 billion deal that would give it greater U.S. control of Corona and other beers. Constellation was to buy the remaining half of a joint venture with Grupo Modelo.

THE ISSUE: The government noted that Anheuser-Busch InBev could end a deal to supply Modelo brands to Constellation after 10 years and retain the Modelo brands and its brewing facilities.