Are supervisors or managers allowed by law to form a union?

FACTS: Supervisors  and managers in petitioner company formed a union separate from that of the rank-and-file union, petitioned for certification election, and staged a strike against the petitioner, prompting the latter to seek a permanent injunction.

HELD:  No. The supervisory employees of petitioner firm may not, under the law, form a supervisors union, separate and distinct from the existing bargaining unit (BEU), composed of the rank-and-file employees of the Bulletin Publishing Corporation. It is evident that most of the private respondents are considered managerial employees. xxx The rationale for this inhibition has been stated to be, because if these managerial employees would belong to or be affiliated with a Union, the latter might not be assured of their loyalty to the Union in view of evident conflict of interests. The Union can also become company- dominated with the presence of managerial employees in Union membership.