In all jurisdictions it is illegal to smoke in a workplace; however, in some industries specifically smoking is permitted in a designated areas only, because, second hand smoke is a bona fide workplace safety hazard.
As with any workplace safety hazard, an employee is protected from reprisal for reporting it to an employer.
If the employee encountered and reprisal or retaliation, the employee would be protected by law and entitled to compensation, restitution, or a combination hereof. More so, the offending party would be liable and subject to fine, penalty, progressive discipline, termination, or combination thereof.
Where this sometimes gets difficult to enforce is if employees are smoking on breaks, say outside the back doors, 15 feet away, and another employee walks past them to get into the building and complains. In that example, the smokers are not doing anything illegal, the complainant just doesn’t like them smoking, but could take a different route into the office.