City Disposal Systems, Inc. (defendant) fired James Brown for refusing to drive a garbage truck another driver had turned in two days before because of faulty brakes. The collective-bargaining agreement (CBA) that covered Brown prohibited the company from requiring employees to drive unsafe trucks, but Brown did not mention it when refusing to drive the truck. Brown filed unfair labor practice charges with the National Labor Relations Board (NLRB) (plaintiff). The NLRB concluded the company fired Brown for concerted activities protected under the National Labor Relations Act (NLRA) and ordered the company to reinstate him with backpay. The appellate court reversed, reasoning the company did not fire Brown for concerted activity because he acted solely on his own behalf. The Supreme Court granted review.