Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 159B, § 6A

No common carrier by motor vehicle shall charge, demand, collect or receive a different compensation for transportation or for any service in connection therewith between the points enumerated in such tariffs than the rates and charges specified in the tariffs in effect at the time; and no such carrier shall refund or remit in any manner or by any device, directly or indirectly, or through any agent or broker or otherwise, any portion of the rates or charges so specified, or extend to any person any privilege or facility for transportation except such as are specified in its tariffs.

No shipper, consignee or any other person, in connection with any transportation operation subject to this chapter, shall knowingly induce or persuade or enter into any contract or agreement with any common carrier by motor vehicle to make a rebate or refund of any lawful transportation charges, or to give up or repay any part of any payment to which he is lawfully entitled, or to render a bill for an amount different from those proper under the rates and charges established under the provisions of this chapter and contained in the published tariffs legally on file with the department.

Nothing in this section shall apply to the transportation of property by motor vehicle when there is a physical transfer of such property from one common carrier to another such common carrier when the rate charged the public for transportation of such property is already published and filed with the department; provided, however, that any person who is an owner-operator of equipment which he rents or leases to a prime contractor, may, solely for the purposes of qualifying for benefits under health and welfare funds and pension funds and for no other purpose be considered an employee of said prime contractor and shall be paid separately for his personal services and separately for the hire of his equipment; provided, further that the total of such payments does not exceed or differ from the compensation for transportation or for any service in connection therewith between the points enumerated in such tariffs; and provided further, that no owner-operator who holds a certificate as a common carrier shall be considered an employee or agent of a contractor for any purpose except that specifically set forth herein nor shall any contractor be held liable in any action of tort arising from the operation of a motor vehicle owned or operated by any such common carrier furnishing transportation services for him.