(dissenting).
i
In a relatively short opinion, the majority concludes that
[t]he issue presented by this case is whether the parties’ past practice is so widely acknowledged and mutually accepted that it amends the contradictory and unambiguous contract language in the collective bargaining agreement. Applying the majority’s analysis and holding in the recently decided Port Huron Ed Ass’n v Port Huron Area School Dist, 452 Mich 309; 550 NW2d 228 (1996), we hold that the association has shown that the parties had a meeting of the minds with respect to the new terms or conditions and that the past practice was so prevalent and widely accepted that *350there was an agreement to modify the contract. Thus, the board of trustees committed an unfair labor practice when it unilaterally changed a mandatory subject of bargaining. [Ante at 340-341.]
n
Although I agree that Port Huron is the proper test, I believe that this case should be remanded to the Michigan Employment Relations Commission. In my opinion, the MERC is in the best position to apply the test which is so clearly delineated in Port Huron.1
The merc is an agency of the Department of Labor whose authority is derived from and governed primarily by the PERA, MCL 423.201 et seq.) MSA 17.455(1) et seq. Section 16 of the pera, which identifies certain types of conduct as *351unfair labor practices, sets forth the procedure for the processing of unfair labor practice charges.
In view of the discretionary authority delegated to the merc in § 16 of the pera, and to the merc hearing referees in the general rules and regulations, it is apparent that the merc’s statutorily mandated function necessarily includes discretion in the substantive resolution of unfair labor practice cases. The merc’s authority is in no way limited to the factfinding function; rather, it continually extends to applying the substantive law in the resolution of claims brought before it. [Smith v Lansing School Dist, 428 Mich 248, 254-258; 406 NW2d 825 (1987).]
When it comes to labor disputes, like the one presented here, the merc is unquestionably the favored body for resolution. In fact, the Legislature has stated that this state favors the resolution of labor disputes through the use of governmental agencies.
It is hereby declared as the public policy of this state that the best interests of the people of the state are served by the prevention or prompt settlement of labor disputes; that strikes and lockouts and other forms of industrial strife, regardless of where the merits of the controversy lie, are forces productive ultimately of economic waste; that the interests and rights of the consumers and the people of the state, while not direct parties thereto, should always be considered, respected and protected; and that the voluntary mediation of such disputes under the guidance and supervision of a governmental agency will tend to promote permanent industrial peace and the health, welfare, comfort and safety of the people of the state. [MCL 423.1; MSA 17.454(1).]
The MERC has been endowed with a large amount of power to help it facilitate the resolution of labor dis*352putes. It can subpoena witnesses, administer oaths, take testimony and receive evidence. MCL 423.11; MSA 17.454(12) provides:
(1) Subject to Act No. 267 of the Public Acts of 1976, the commission and each commissioner and each person designated by the commission may hold public or private hearings within the state, subpoena witnesses and compel their attendance, administer oaths, take testimony, and receive evidence. A subpoena may be issued only after the mediation of a dispute shall have been actually undertaken.
(2) If a person is contumacious or refuses to obey a subpoena issued to the person, the circuit court of a county within the jurisdiction of which the inquiry is carried on, upon application by the commission, may issue to the person an order requiring the person to appear before the commission, to produce evidence or to give testimony touching the matter in question. Failure to obey an order may be punished by the court as contempt.
In the instant matter, the MERC had an opportunity to examine the relevant Detroit Charter:2
Contrary to the holding of the [hearing referee], we find in favor of the Charging Party. Past practice, the opinions of Corporate Counsel, the opinion of legal counsel for the Board of Trustees, and a Circuit Court decision all establish that the Medical Board of Review is the final arbiter of whether an injury/illness is duty related.
Pensions and the significant provisions of a pension plan are mandatory subjects of bargaining. Detroit Police *353Officers Ass’n v Detroit, 391 Mich 44 [214 NW2d 803] (1974). We find in the case before us that the board which determines eligibility for a duty-related pension is a significant provision in the Detroit pension plan and is a mandatory subject of bargaining. The unilateral change of that mandatory subject effectuated by the December 6, 1990, resolution is an unfair labor practice. [1993 MERC Lab Op 424, 432.]
However, when the MERC originally heard this case, it did not have the benefit of the standard offered in Port Huron. As a result, its decision was not based on the proper foundation. Consequently, it now makes perfect sense to allow the merc the first opportunity to apply the new standard from Port Huron.
This conclusion is further buttressed by the fact that the merc has been charged with the responsibility to see a case to resolution.
Rather, we read pera and related state statutes as manifesting a clear legislative intent that, once a party to a public sector employment collective bargaining relationship invokes merc’s jurisdiction under pera, that party’s complaint should be resolved by merc in accordance with the statutory processes. [Detroit Fire Fighters Ass’n v Detroit, 408 Mich 663, 685; 293 NW2d 278 (1980).]
HI
The merc did come to a resolution of this case before it was appealed to this Court, but that resolution did not apply the new standard. Because the merc is in the position of factfinder and because it has the responsibility to resolve labor disputes in accordance with statutory process, I favor remanding the case to the MERC while retaining jurisdiction.
Brickley, C.J., and Weaver, J., concurred with Riley, J.In Port Huron, this Court stated:
Where unambiguous language in the agreement conflicts with the past practice of the parties, however, a higher standard of proof is required.
“The highest quantum of proof will ordinarily be required in order to show that the parties intended by their conduct to amend or modify clear and unambiguous contractual language, however.” [Total Petroleum, Inc v Int’l Union of Operating Engineers, Local 670, 78 Lab Arb (BNA) 729, 737 (Roberts, 1982).]
The party seeking to supplant the contract language must submit proofs illustrating that the parties had a meeting of the minds with respect to the new terms or conditions — intentionally choosing to reject the negotiated contract and knowingly act in accordance with the past practice. See Elkouri & Elkouri [How Arbitration Works (4th ed)], p 455. In such situations, it is the underlying agreement to modify the contract that alters the parties’ obligations, not the past practice. Ford Motor Co v United Automobile, Aircraft & Agricultural Workers, Local 600, 19 Lab Arb (BNA) 237, 241-242 (Shulman, 1952). [Port Huron, supra at 328-330 (Boyle, J.)]
The Detroit Charter provides in relevant part:
If a member shall become totally incapacitated for duty by reason of injury, illness or disease resulting from the performance of duty and if the Board of Trustees shall find such injury, illness or disease to have resulted from the performance of duty, . . . such member shall be retired .... [Detroit Charter, tit IX, ch VH, art VI, part B, § 1.]