Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 150A, § 10

(a) Wherever the application of the provisions of any other law of this commonwealth conflicts with the application of the provisions of this chapter, this chapter shall prevail.

(b) This chapter shall not be deemed applicable to any unfair labor practice involving employees who are subject to and protected by the Federal Railway Labor Act,  1 or to any unfair labor practice governed exclusively by the national labor relations act or other federal statute or regulations issued pursuant thereto, unless the federal agency administering such act, statute or regulation has declined to assert jurisdiction thereof, or except where such federal agency has conceded to the commission jurisdiction over any such case or proceedings.