This law applies when an employee or former employee files a suit against either the union or employer. It also applies in a hybrid suit against the employer and union. A plaintiff may decide to sue one defendant and not the other, but must prove the same case whether the suit is against one defendant or both. SEE Chauffeurs, Teamsters and Helpers Local No. 391 v. Terry, 494 U.S. 558, 564 (1990) (explaining that most collective bargaining agreements accord finality to grievance procedures established by the agreement).To support a breach of the duty of fair representation claim, you must prove that the employer’s action violated the terms of the collective bargaining agreement and that the union breached its duty to act honestly and in good faith and to avoid arbitrary conduct. Id. at 563; see also Hines v. Anchor Motor Freight, 424 U.S. 554, 564 (1976) (union is always subject to complete good faith and honesty of purpose in the exercise of its discretion); Vaca v. Sipes, 386 U.S. 171, 177 (1967).A union is not liable for merely negligent conduct. See United States Steelworkers of Am. v. Rawson, 495 U.S. 362, 372-73 (1990); Slevira v. Western Sugar Co., 200 F.3d 1218, 1221 (9th Cir.2000). Breach of the duty of fair representation occurs only when a union’s conduct is arbitrary, discriminatory, or in bad faith. See id. For example, "[a] union breaches its [duty of fair representation] if it ignores a meritorious grievance or processes it in a perfunctory manner." Conkle v. Jeong, 73 F.3d 909, 916 (9th Cir.1995) (citing Vaca, 386 U.S. at 191).A union’s actions are arbitrary "only if, in light of the factual and legal landscape at the time of the union’s actions, the union’s behavior is so far outside a ‘wide range of reasonableness’ as to be ‘irrational.’" Air Line Pilots Ass’n v. O’Neill, 499 U.S. 65, 67 (1991). See also Conkle, 73 F.3d at 915-16 (holding that a union’s decision is arbitrary if it lacks a rational basis); Johnson v. United States Postal Serv., 756 F.2d 1461, 1465 (9th Cir.1985) (holding that reckless disregard may constitute arbitrary conduct); Tenorio v. NLRB
, 680 F.2d 598, 601 (9th Cir.1982) (defining arbitrary as the "egregious disregard for the right of union members").To establish that a union acted in "bad faith," a plaintiff must provide "substantial evidence of fraud, deceitful action, or dishonest conduct," Humphrey v. Moore, 375 U.S. 335, 348 (1964), or evidence that the union was motivated by personal animus toward the plaintiff. See Conkle, 73 F.3d at 916 (including personal animus as basis for finding of bad faith).