Not enough information. Is he on an open work permit or on a closed work permit tied to a specific employer?
If he is on a closed work permit tied to a specific employer - then he can look for a new job, but he cannot start a new job using his current work permit. Once he finds his new job, his new employer will need to get an approved LMIA and then he will need to apply for a new work permit. Once the new work permit is approved, he will be able to start his new job.
