In California, at least, it is required. The owner is responsible for the employees' work. The employees don't have to be licensed, so the employer must be. An

In California, at least, it is required. The owner is responsible for the employees' work. The employees don't have to be licensed, so the employer must be. An apprenticeship is mandatory, in California. You have to be employed by a licensed contractor for 4 years and be able to prove it (timecards, etc).