Short answer. No. Article 280 of the Labor Code applies "the provisions of written agreement to the contrary notwithstanding," so a company policy cannot override it. If your work is usually necessary or desirable to the employer's business, or you have served at least one year, the law treats you as regular regardless of the policy.
What the law says
The provisions of written agreement to the contrary notwithstanding and regardless of the oral agreement of the parties, an employment shall be deemed to be regular where the employee has been engaged to perform activities which are usually necessary or desirable in the usual business or trade of the employer
Labor Code, Article 280 — Regular And Casual Employment. Read the full provision →
The article overrides contrary agreements by its own terms
Article 280 opens by stating that regular status attaches the provisions of written agreement to the contrary notwithstanding and regardless of the oral agreement of the parties. That language exists precisely to stop employers from contracting around regularization — a policy manual, employment contract clause, or company rule declaring that no one ever becomes regular does not have legal effect if the work itself meets the article's test.
What actually makes employment regular
The test is functional, not contractual: employment is regular where the employee has been engaged to perform activities which are usually necessary or desirable in the usual business or trade of the employer. If your tasks are part of what the business ordinarily does to operate, the nature of the work — not a label the employer attaches to your position — is what the statute looks at.
The article does carry genuine exceptions, and they are what employers should be relying on if anything: work fixed for a specific project or undertaking the completion or termination of which has been determined at the time of the engagement, and work that is seasonal in nature for the duration of the season. Note when the project has to be defined — at engagement. A project label pinned on afterwards, or renewed indefinitely, is not what the exception describes.
The one-year rule as a second path to regular status
Article 280 also provides that any employee who has rendered at least one year of service, whether such service is continuous or broken, shall be considered a regular employee with respect to the activity in which he is employed. This applies even to employment initially treated as casual, giving a second route to regular status independent of whether the job itself was "usually necessary or desirable" from day one.
What to gather if your employer relies on such a policy
Keep records of what your actual duties are and how long you have worked, since both the nature-of-work test and the one-year rule turn on facts a policy statement cannot erase. A written policy declaring no one becomes regular is worth noting, but it is the underlying work and tenure that a lawyer will look at in assessing whether Article 280 already applies to you regardless of it.
The one-year route has a shape of its own, too. It makes the employee regular with respect to the activity in which he is employed, and the employment shall continue while such activity exists — so it is tied to the work actually being done rather than conferring a post in the abstract. Service counts whether continuous or broken, which is why a run of short contracts with gaps engineered between them does not reset the clock.