What constitutes the basis of a matter of mutual interest is not defined within the provisions of the Labour Relations Act, but rather subject to interpretation on a case-to-case basis. What constitutes a mutual interest can broadly be understood as any action or conduct which has the propensity to affect the employment relationship between the employer and employee(s). The most commonly accepted mutual interest is unilateral changes to the employment conditions.
In Rand Tyres & Accessories v Industrial Council for the Motor Industry 1941 TPD 108 the Court interpreted mutual interest in the broadest sense as:
“Whatever can be fairly and reasonably regarded as calculated to promote the well-being of the trade concerned, must be of mutual interest to them.”
In Department of Home Affairs v Public Servants Association and Others  ZACC 11 The Court held:
“What constitutes a matter of mutual interest is not defined in the LRA. The term serves to define the legitimate scope of matters that may form the subject of collective agreements, matters which may be referred to the statutory dispute‑resolution mechanisms, and matters which may legitimately form the subject of a strike or lock‑out.”
“Interest” and “rights” disputes may both be matters of mutual interest:
Referral of mutual interest disputes coincides with strike action; the purpose of this article is to set out when the right to strike in terms of Section 64 is not protected in terms of a referral for mutual interest.
Interpretation of mutual interest disputes
In Ceramic Industries Ltd t/a Betta Sanitaryware & another v NCBAWU & others  6 BLLR 697 the Labour Appeal Court held that a strike over a demand calling for the dismissal of an employee was unprotected.
In Mawethu Civils (Pty) Ltd v National Union of Mineworkers and Others (Case no: PA2/14) the Court held that the issue in dispute involves an alleged unfair labour practice which could and should have been referred to the CCMA in terms of s191(1)(a) of the LRA. If and when conciliation failed, the employees would at that point have acquired the right to request that the matter be arbitrated in terms of s191(5)(iv) of the LRA.
Section 65(3) of the Labour Relations Act imposes a statutory limitation on the right to strike where the nature of the dispute is one which can be referred to arbitration or adjudication.
The issue of whether the right to refer a dispute for mutual interest in view of strike action where the referring party demands recourse which is unlawful was determined in the case of TSI Holdings (Pty) Ltd v National Union of Metalworkers of SA , in this case the referring party, referred a dispute of mutual interest demanding the employer remove a supervisor for alleged racial slurs. On appeal the Labour Appeal Court considered the true nature of the employees demands, and held that the demands were unlawful in that had the employer acted on the demands it would have resulted in the infringement of the statutory right to a fair hearing for the supervisor to which the employees alleged carried out racial slurs. In the Appeal Courts ruling the right to strike was unprotected.
Where the demands would violate any rights protected in terms of the Labour Relations Act or any supporting legislation would render the demands unlawful and any subsequent strike action unprotected.