In the Philippine legal landscape, the tension between an employee's right to work and an employer’s duty to maintain a safe workplace is governed by the Labor Code, Occupational Safety and Health (OSH) Standards, and various administrative issuances from the Department of Labor and Employment (DOLE).

1. The Management Prerogative

Under Philippine jurisprudence, employers possess "management prerogatives"—the right to regulate all aspects of employment according to their own discretion and judgment. This includes health and safety protocols. An employer has the legal right (and obligation) to bar an employee from the physical workplace if their presence poses a threat to:

The health and safety of the sick employee.
The health and safety of co-workers.
The general public or clients.

2. General Duty Clause (RA 11058)

Republic Act No. 11058, or the Occupational Safety and Health Standards Act, mandates that every employer shall provide a place of employment that is free from hazardous conditions.

Safety as a Priority: If an employee is visibly ill or carries a communicable disease, allowing them to remain on-site may be considered a violation of the employer’s duty to maintain a safe environment.
Right to Refuse Unsafe Work: While usually applied to employees, the principle extends to the environment; an employer can proactively prevent "unsafe" human conditions (like a contagious illness) from compromising the workplace.

3. Standards for "Fitness to Work"

The primary mechanism for preventing a sick employee from working on-site is the Medical Certificate.

Fitness Assessment: An employer can require an employee to undergo a medical examination or present a "Fit to Work" clearance from a company physician or a licensed doctor.
Suspicion of Illness: If an employee shows symptoms (e.g., high fever, persistent coughing, or infectious rashes), the employer can legally direct the employee to go home and seek medical consultation before returning.

4. Communicable Diseases and Specific Mandates

The Department of Health (DOH) and DOLE have specific guidelines for certain illnesses (e.g., Tuberculosis, HIV/AIDS, Hepatitis B, and more recently, COVID-19/Respiratory illnesses).

Mandatory Isolation: For highly contagious diseases, the employer is legally bound to enforce isolation or quarantine protocols dictated by the government.
Non-Discrimination: While an employer can prevent an employee from working on-site, they cannot terminate the employee solely based on a disease unless it is prohibited by law or if the disease cannot be cured within six months and is prejudicial to the employee's health or that of their co-workers (Art. 299, Labor Code).

5. Leaves and Compensation

When an employer prevents an employee from working on-site due to illness, the following rules generally apply:

Sick Leave Utilization: The period of absence is usually charged against the employee’s accrued sick leave credits.
No Work, No Pay: If sick leave credits are exhausted, the "no work, no pay" principle generally applies, unless a Collective Bargaining Agreement (CBA) or company policy states otherwise.
Telecommuting: Under the Telecommuting Act (RA 11165), if the nature of the job allows, the employer and employee may agree to a work-from-home arrangement so the employee can remain productive without physical presence on-site.

6. Procedural Due Process

To avoid claims of illegal "constructive dismissal" or harassment, employers must:

Have a Clear Policy: Outline health-related protocols in the Employee Handbook.
Apply Fairly: Ensure the policy is applied to all levels of staff without discrimination.
Documentation: Formally document the observation of symptoms and the instruction to leave the premises to justify the action.

Summary of Legal Basis

Legal Reference	Application
Art. 299, Labor Code	Termination due to disease (as a last resort).
RA 11058 (OSH Law)	Duty to provide a safe, hazard-free workplace.
RA 11165	Basis for remote work as an alternative to on-site presence.
Management Prerogative	The inherent right to control workplace entry for safety.