"Brother," above, was right when he said licensing requirements vary from state to state. And, "licensed" and "qualified" are two way different things. An electrician who's been doing residential wiring for 10 years is proabably not be qualified to open a 480V switchgear.
Here's what I found of the Michigan law:
338.887 Electrical contractor's license requirements; exceptions.
Sec. 7.
(1) Except as otherwise provided in this act or in subsection (3), a person shall not engage in the business of electrical contracting unless the person has received from the board or from the appropriate municipality an electrical contractor's license.
(2) Except as otherwise provided in this act or in subsection (3), an individual, other than an individual who is licensed under this act and employed by and working under the direction of a holder of an electrical contractor's license, shall not in any manner undertake to execute any electrical wiring [with certain exceptions].
The first part has to do with contracting, the second part says unlicensed persons can't do "electrical wiring." Sec. 1 of the act defines "wiring" as "all wiring, generating equipment, fixtures, appliances, and appurtenances in connection with the generation, distribution, and utilization of electrical energy, within or on a building, residence, structure, or properties, and including service entrance wiring as defined by the code."
The best interpretation can only come from the Michigan electrical administrative board.