Mass. Gen. Laws ch. 253 § 2
Such dam shall not be erected to the injury of a mill lawfully existing above or below it on the same stream, nor to the injury of a mill site on the same stream on which a mill or mill dam has been lawfully erected and used, unless the right to maintain a mill on such last mentioned site has been lost by abandonment or otherwise; nor shall a mill dam be erected or raised to the injury of any such mill site which has been occupied as such by the owner thereof, if, within a reasonable time after commencing such occupation, he completes and puts in operation a mill for the working of which the water of such stream is applied; nor shall a mill or dam be placed on the land of any person without such grant, conveyance or authority from the owner as would be necessary to convey land.
Mass. Gen. Laws ch. 253, § 2