Code of Alabama
Chapter 37 - Plumbers and Gas Fitters.
Section 34-37-16 - Restrictions.

(a) No person shall use nor allow their certificate to enable anyone other than the certificate holder and his or her employees directly supervised by the certificate holder to perform plumbing or gas fitting. Local officials may require the certificate holder to be present if any problems develop on the work.
(b) No certificate issued by the board can be sold or transferred. Any certificate which is misused may be revoked by the board.