Legal Question in Employment Law in Massachusetts

It is inappropriate and most likely a violation of your contract with the union as well as a violation of a number of laws. If the union has an objection to a hire by the company under the CBA the steward and the union rep are supposed to file the appropriate objection and claim. if not satisfied with the company response they go to arbitration or such other process provided under the CBA. . Trying to dissuade a job applicant because the steward believes the hire is not permitted under the agreement could be considered tortuous interference with the employer's business. If you want to pursue this I suggest you contact an attorney who specializes in labor law.