29 CFR 29.11: Limitations.

Nothing in this part or in any apprenticeship agreement will operate to invalidate:

(a) Any apprenticeship provision in any collective bargaining agreement between employers and employees establishing higher apprenticeship standards; or

(b) Any special provision for veterans, minority persons, or women in the standards, apprentice qualifications or operation of the program, or in the apprenticeship agreement, which is not otherwise prohibited by law, Executive Order, or authorized regulation.