Short answer. Voluntary as a rule, but not absolutely. Article 70 makes the organisation of apprenticeship programmes primarily a voluntary undertaking by employers, while allowing the President to require compulsory training in certain trades where a shortage of trained manpower is critical, as determined by the Secretary of Labor.
What the law says
The organization of apprenticeship program shall be primarily a voluntary undertaking by employers
Labor Code, Article 70 — Voluntary Programs And Exceptions. Read the full provision →
“Primarily” is carrying the weight
The article does not say apprenticeship is voluntary; it says it is primarily a voluntary undertaking, and then sets out when it is not. That word is the hinge. The default is that an employer decides for itself whether to train apprentices at all, because a programme it was forced into is unlikely to be a good one. But the default gives way where the country's need for trained people in a particular trade is judged critical, and the article provides the machinery for that.
When training can be made compulsory
The power belongs to the President, exercisable when national security or particular requirements of economic development so demand, over certain trades, occupations, jobs or employment levels where the shortage of trained manpower is deemed critical. The determination of criticality is made by the Secretary of Labor and Employment, and appropriate rules are promulgated by the Secretary as the need arises. So compulsion is not something a local office can impose on a single company it thinks ought to be training more people. It is targeted at a trade, not at an employer.
The foreign technician exception
The article carries one further requirement that operates on its own terms: where the services of foreign technicians are used by private companies in apprenticeable trades, those companies are required to set up appropriate apprenticeship programmes. This does not depend on any presidential issuance. It reflects a simple policy — a company importing skill in a trade that can be taught here should be building that skill locally at the same time — and it is the provision most likely to bite in practice.
What it means for a worker
Do not expect this article to give you a right to be trained. It regulates whether programmes exist, not who gets into one, and no employee can invoke it to require an employer to open a programme for them. Where it becomes useful is in understanding the programme you are already in: whether the employer took it on voluntarily, and which rules the programme is supposed to be running under. The apprenticeship agreement, and the programme's recognition, are the documents to ask for.