It shall be an unfair labor practice for a labor organization to refuse to bargain collectively with any employer who has recognized it as the exclusive representative of employees in a unit appropriate for the purposes of collective bargaining.
Mass. Gen. Laws ch. 150A, § 4B
Refusal to bargain collectively with employer
Official source: Massachusetts Legislature. Reproduced from public-domain Massachusetts statutes; confirm against the official source for the current text. Not legal advice.