arbiter

arbiter
/ˈɑ:bɪtə(r); `ɑrbɪtɚ/ n
1 ~ (of sth) person who has power to decide what will be done, accepted, etc with regard to sth （对某事物有权决定处理, 认可等的）仲裁人; 裁决人; 权威人士
    the arbiters of fashion 时装的权威.
2 (dated or Scot 旧或苏格兰) = arbitrator.

牛津英汉双解词典