Usage patterns
〈人〉が労働組合に加入するfor someone to join a labor union
The new employee joined the labor union right after starting work.
労働組合を結成するto form a labor union
The employees formed a labor union to demand better working conditions.
労働組合と交渉するto negotiate with the labor union
Management negotiated with the labor union over a pay raise.
労働組合が〈事〉を要求するfor a labor union to demand something
The labor union demanded a reduction in overtime hours.