There is no law against this. The fact is that in an "at will" employment arrangement, a company can set the conditions of the workplace much as it sees fit. This includes having a new hire come in with the same job title as existing employees and making the same salary. Unless this action in some way constitutes legally actionable discrimination or violates a union agreement or employment contract, it is perfectly permisable. At this point, your union rep will have to adise you further.