G.R. No. 110399 - San Miguel Corp. Supervisors and Exempt Union vs. Laguesma

On October 5, 1990, the San Miguel Corporation Supervisors and Exempt Union filed with DOLE a Petition for District Certification or Certification Election among supervisory and exempt employees of the SMC Magnolia Poultry Products Plants in Cabuyao, San Fernando, and Otis.
On December 19, 1990, Med-Arbiter Danilo L. Reynante ordered a single certification election covering all three plants as one bargaining unit.

On January 18, 1991, San Miguel Corporation appealed, challenging the grouping of the three separate plants into one unit and the inclusion of supervisory levels 3 and 4 (confidential positions).
On July 23, 1991, Undersecretary Bienvenido E. Laguesma granted the appeal and remanded for proper classification of employees.
On September 3, 1991, upon union reconsideration, Undersecretary Laguesma directed separate elections for supervisors levels 1–4 and exempt employees in each plant.
On September 21, 1991, the company moved for reconsideration and to suspend proceedings.
On March 11, 1993, Undersecretary Laguesma issued an order, relying on Philips Industrial Development, Inc. v. NLRC, excluding supervisory levels 3 and 4 and exempt employees as confidential, thereby barring them from the certification election.

Are supervisory employees levels 3 and 4 and the exempt employees “confidential employees” under the Labor Code, thus ineligible to join or form a labor union?
If they are not confidential employees, should the employees of the three Magnolia Poultry plants constitute one appropriate bargaining unit?