The National Labor Relations Board ruled Thursday that pharmaceutical company Pfizer cannot compel workers not to join their fellow employees in organized disputes with the company. The ruling stems from a complaint filed at a Pfizer plant in Kalamazoo, MI in which the company insisted workers agree not to file class actions suits against Pfizer with the NLRB. The Board ruled that such practices are akin to the "yellow dog' contracts of the early part of the last century, in which employees were forced to agree not to unionize. Pfizer plans on appealing the ruling, while the U.S. Supreme Court has announced it will rule on three cases centered on the very same issue.