What is the test for statutory intent to restrict the general common law principle of the right to trade freely?

It is always open to the legislative authority to restrict that general common law principle by statutory enactment where it considers it appropriate to do so, and thus restrict that individual liberty of action. However, any statute which purports to modify what was hitherto a part of the common law, such as the right to trade freely, must be clear and distinct in its intention so to do, and in the absence of a concise and unambiguous declaration of intention in the statute, there is no presumption, whether by inference or otherwise, that the common law is to be altered: Craies on Statute Law, 5th ed. (1952), p. 114-5, p. 310; Leach v. Rex, [1912] A.C. 305 at p. 311.