Why Is Canopy Growth (CGC) Stock Plunging 20% Today? Source: T. Schneider | Shutterstock Canopy Growth (NASDAQ: CGC ) stock is falling on Thursday following an update that Constellation Brands (NYSE: STZ ) has reached an agreement to eliminate its Class B shares . This agreement was suggested by a committee made up of independent directors from Constellation’s Board. That has the company’s Board advising shareholders to vote in favor of eliminating its Class B shares. Constellation Brands says that this agreement was reached with members of the Sands Family. If approved, it would result in Class B shareholders having to trade in their stock for cash or a mix of stock and cash. The company is offering up to $1.5 billion in cash, or one share of STZ stock and $64.64 in cash for each share of Class B stock converted. So what does this have to do with Canopy Growth? Constellation Brands owns a large stake in the marijuana company. With the change in how its shares are listed, shares of CGC stock are sliding as well. But there’s more to it than that.