Short answer. Not if the order really was unlawful. The just cause is wilful disobedience of a lawful order connected to your work, so an instruction that is itself illegal cannot support dismissal for refusing it. The difficulty is proving the order was unlawful rather than merely unwelcome.
What the law says
Serious misconduct or willful disobedience by the employee of the lawful orders of his employer or representative in connection with his work
Labor Code, Article 282 — Just Causes For Dismissal. Read the full provision →
Lawfulness is built into the ground itself
The article does not permit dismissal for disobedience at large. It permits dismissal for wilful disobedience of the lawful orders of his employer. Lawfulness is therefore not a defence you raise against an otherwise complete ground — it is part of what the employer has to establish before the ground exists at all. If the instruction was to falsify a record, conceal a violation, or do something the law forbids, refusing it does not become a dismissible offence merely because a superior gave it.
Believing it was illegal is not the same as it being illegal
This is where most of these cases actually turn. A sincere belief that an order was improper does not, by itself, take the order outside the article. What matters is whether the instruction was in fact contrary to law or otherwise beyond what the employer may lawfully require. Orders that are inconvenient, unfair-feeling, contrary to custom, or simply outside what you were used to doing are not unlawful in this sense, and refusing them squarely raises the disobedience question.
The refusal must also have been wilful
Even where an order is lawful, the article requires disobedience that is wilful — a deliberate, perverse refusal rather than a misunderstanding, an inability to comply, or a request for clarification. Someone who asks for the instruction in writing, or who flags a legal concern and asks to be told to proceed anyway, is behaving very differently from someone who simply refuses. How you framed the refusal at the time is often the single most important fact in the record.
Get the instruction and your objection in writing
If you are asked to do something you think is unlawful, the most useful thing you can do is create a written trace before the confrontation hardens: ask for the instruction by message or email, and state your concern in the same channel. That converts a contested memory into a document. Keep the notice to explain, your written reply, and anything showing what the instruction actually required, and take advice on whether the order was genuinely unlawful before assuming it was. Put the refusal and its reason in writing at the time, however briefly. A contemporaneous note is worth more later than any recollection.