Under Philippine labor law, a strike is the concerted work stoppage undertaken by employees to enforce demands against their employer regarding employment terms and conditions. Strikes are governed primarily by the Labor Code of the Philippines (particularly Book V, Title VII) and various implementing rules and regulations. While the law respects the right of workers to engage in concerted activities, it sets stringent procedural and substantive requirements to ensure that strikes are lawful. When these requirements are not met, a strike is deemed illegal. Participation in an illegal strike can serve as a valid ground for termination, subject to both substantive and procedural due process requirements set forth by the Labor Code and Department of Labor and Employment (DOLE) issuances, including Department Order (D.O.) No. 147-15.

1. Legal Framework and Governing Principles

Constitutional Underpinnings: The 1987 Philippine Constitution guarantees the rights of workers to self-organization, collective bargaining, and peaceful concerted activities, including the right to strike. However, the exercise of this right is not absolute. The State may regulate strikes to protect public interest, ensure the orderly exercise of the right, and maintain industrial peace.
Labor Code Provisions: The Labor Code sets forth the legal requisites for a valid strike. Generally, for a strike to be lawful, it must:
1. Be based on a legitimate ground, such as a collective bargaining deadlock or unfair labor practice (ULP) committed by the employer.
2. Comply with procedural requirements: the filing of a notice of strike with the National Conciliation and Mediation Board (NCMB), observance of a prescribed cooling-off period (30 days for bargaining deadlocks, 15 days for ULPs), the conduct and majority approval of a strike vote by secret ballot, and proper notice of the results of the strike vote.
3. Occur after conciliation and mediation efforts have failed to resolve the dispute.

If these conditions are not satisfied, the strike is considered illegal. Strikes that violate a no-strike clause in a collective bargaining agreement (CBA), are staged without the required notice, or defy the assumption or certification order of the Secretary of Labor and Employment (who may direct parties to desist from or resume operations in critical industries) are also illegal.

2. Grounds for Declaring a Strike Illegal

A strike can be deemed illegal for various reasons, including but not limited to:

Lack of a Valid Cause: Staging a strike for reasons not authorized by the Labor Code, such as trivial grievances or purely political motivations.
Non-Compliance with Procedural Requirements: Failure to file the required notices, hold a valid strike vote, or observe the mandated cooling-off period.
Defiance of Government Intervention: Once the Secretary of Labor and Employment assumes jurisdiction over a labor dispute in an industry indispensable to the national interest, or certifies it to the National Labor Relations Commission (NLRC), any strike staged thereafter is illegal.
Illegal Acts During a Strike: Even if the strike was initially legal, the commission of illegal acts (e.g., violence, sabotage, serious property damage, intimidation, or preventing willing workers and suppliers from entering the premises) can render it illegal.

3. Consequences of Participation in an Illegal Strike

Participating in an illegal strike may constitute a just cause for termination of employment. Under the Labor Code and long-established Supreme Court jurisprudence, employees who engage in an illegal strike may lose their employment status. The employer, however, must observe due process and must differentiate between union officers and ordinary union members:

Union Officers: Officers of a union bear a higher degree of responsibility. If they knowingly participate in or lead an illegal strike, their acts are considered serious misconduct. They may be validly terminated from employment without a corresponding obligation on the part of the employer to reinstate them.
Ordinary Union Members: For rank-and-file employees who join an illegal strike, the law and jurisprudence are somewhat more lenient. Mere participation by rank-and-file members in an illegal strike may be a ground for disciplinary action, including dismissal, but the Supreme Court has repeatedly emphasized that reinstatement may be possible if the employees apply for re-employment and express genuine remorse or willingness to comply with lawful management directives. Nevertheless, if they committed illegal acts (such as violence, coercion, or preventing non-strikers from working) during the strike, termination may be justified.

4. Legal Basis for Termination: Just Cause vs. Authorized Cause

The Labor Code distinguishes between “just causes” and “authorized causes” for termination. Strictly speaking, participation in an illegal strike is typically addressed under just causes for termination—not authorized causes. Just causes (Art. 297 [formerly Art. 282] of the Labor Code) include serious misconduct, willful disobedience, gross and habitual neglect of duties, fraud, breach of trust, and commission of a crime against the employer or co-employees, among others.

Engaging in an illegal strike often falls under serious misconduct or willful breach of discipline because it contravenes the lawful processes provided by the Labor Code. Although the user’s categorization may place illegal strike under “Authorized Causes” as per a given outline, it is traditionally understood as a just cause for dismissal. This discrepancy may arise from the manner in which references or outlines are organized. Nonetheless, from a doctrinal standpoint, illegal strikes serve as a just cause for termination rather than an “authorized cause” (which usually pertains to economic or business-related grounds, like retrenchment, redundancy, closure, or disease).

5. Procedural Due Process Requirements Under Department Order No. 147-15

DOLE Department Order No. 147-15 provides guidelines on the procedural aspects of termination for just and authorized causes. The twin requirements of notice and hearing must be observed even when terminating employees for participating in an illegal strike:

First Notice (Notice to Explain/Show Cause): The employer must issue a written notice informing the employee of the specific grounds (e.g., participation in an illegal strike), the acts constituting the violation, and giving the employee an opportunity to submit a written explanation.
Hearing or Conference: The employee must be given a reasonable chance to respond, present evidence, and defend themselves against the accusation. This can be done through a formal hearing or a less formal conference, provided the employee’s right to due process is upheld.
Second Notice (Notice of Decision): After considering the employee’s explanation and any evidence presented, the employer must issue a second written notice, stating clearly the decision to terminate (or otherwise discipline) the employee, the reasons for such decision, and the effective date of termination.

Failure to comply with these procedural requirements does not invalidate the just cause for termination but may render the employer liable for nominal damages due to violation of due process rights.

6. Burden of Proof and Evidentiary Matters

The employer bears the burden of proving that:

The strike was illegal.
The employee knowingly and actively participated in the illegal strike or committed illegal acts therein.

Solid proof—such as documentary evidence, eyewitness accounts, or official findings of labor authorities—is critical. If the employer cannot substantiate the allegations, the employee should not be dismissed.

7. Judicial and Quasi-Judicial Precedents

The Supreme Court of the Philippines has consistently upheld the employer’s right to dismiss employees who take part in illegal strikes, especially union officers who orchestrate such strikes. Key rulings have reiterated that the right to strike is not a license to violate legal prerequisites, and that employees must exercise their collective actions within the bounds of law. Courts generally balance the rights of employees with the employer’s prerogatives and the broader national interest in stable industrial relations.

However, courts also stress that not all participants in an illegal strike should automatically be terminated. The degree of involvement, the presence (or absence) of violence, and the timeliness of employees’ willingness to return to work are considered. The “plain members” who were merely misled into joining may be shown leniency under certain circumstances.

8. Reinstatement and Post-Strike Resolution

Depending on the severity of the illegal strike and the employer’s discretion, employees who participated may be reinstated if they show good faith, apply for reemployment, and commit to respecting lawful processes going forward. If the employer refuses reinstatement, the matter may be challenged before the NLRC or the appellate courts, which will evaluate whether the penalty of dismissal was commensurate to the offense and whether due process was observed.

9. Interaction with Collective Bargaining and Industrial Harmony

The regulation of strikes, particularly the illegality of those conducted in violation of the Labor Code, aims to maintain industrial peace and protect the economic survival of enterprises. By penalizing illegal strikes, the law encourages unions and employers to resolve their disputes through legally prescribed mechanisms—conciliation, mediation, voluntary arbitration, and other dispute-resolution procedures—before resorting to disruptive work stoppages.

In Summary:

Participation in an illegal strike constitutes a serious violation of the Labor Code’s prescriptions for lawful concerted activity. Union officers who knowingly lead or participate in an illegal strike may be terminated from employment. Rank-and-file employees who join an illegal strike may also face dismissal but, depending on the circumstances, may be reinstated if they demonstrate a willingness to abide by the law and the directives of the employer. The termination process must comply with the procedural due process requirements set out in D.O. No. 147-15, which mandates proper notice, a fair hearing, and the issuance of a written decision. Ultimately, the strict regulation of illegal strikes reflects the State’s effort to balance workers’ rights with the need for industrial peace, economic stability, and respect for the lawful processes that govern labor relations in the Philippines.