As an L-2 spouse he is authorized to work incident to his status, with the annotated I-94 serving as evidence for employers. Whether he can practise a licensed trade depends on the destination state’s licensing rules, which are separate from immigration.
Work authorization is the easy part; the trade licence is the hard part
L-2 spouses have employment authorization incident to status, so once admitted with the properly annotated Form I-94 he can accept employment or run his own business without waiting for a separate employment document. That answers the immigration question. It does not answer whether a Canadian journeyman electrician, plumber or gasfitter may work unsupervised in the state where the plant sits, because trades are licensed by states and sometimes by counties, and reciprocity with Canadian certification varies.
Ask the state licensing board in writing what it accepts and how long an examination takes, and plan for a period in which he works under a licensed contractor. Children may enrol in school but cannot work in L-2. Each dependant’s status ends when the principal’s ends, so his business plans should assume the L-1A timeline, including the seven-year maximum, rather than an indefinite stay.
If the household hopes for permanent residence later, that is a separate analysis. A first review separates immigration permission from the local rules governing the spouse’s proposed work and records each dependant’s end date. Hypothetical example: an L-1A recipient’s partner wants to open a mobile hearing-test business.
The admission record resolves work authorization, while state professional rules and business registration resolve whether services can begin. Sequence immigration admission first, then licensing and commercial setup, rather than advertising services before the necessary local permissions exist.