Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 90, § 40B

All airport approach regulations adopted under this chapter shall be reasonable, and no such regulation shall require the removal or lowering, or other change or alteration, or prohibit the repair or replacement, of any structure or tree not conforming to the regulations when adopted or amended, or otherwise interfere with the continuance of any such non-conforming structure or tree, except as provided in section forty G.