In New South Wales the legislature intervened as early as 1858 to restrain the development of the notion that permissive words may have a compulsive effect and, by 22 Vict. No. 12, s. 8, declared that wherever in an Act a power is conferred on any officer or person by the word "may" or the words "it shall be lawful" or "it shall and may be lawful" such words shall mean that the power may be exercised or not at discretion, a provision now contained in s. 23 of the Interpretation Act of 1897 but restricted to the word "may": see Smith v. Watson [2] and Re Fettell [3] . The words "at discretion" are strong and, though it may readily be conceded that the section lays down a rule of construction which like other rules of construction will give way to clear indications of a contrary intention, there must be reasons which satisfy the mind that a statute to be construed does not intend that the power it confers should be exercised or not at discretion before it can be held that the power must be exercised on demand, assuming of course the fulfilment of any conditions precedent the statute may lay down. A distinction obviously exists between the possession by a person interested, on the one hand, of a right to call upon the officer upon whom a power is conferred to exercise his discretion and, on the other hand, of a right to call upon him to exercise the power. The former means no more than that, when called upon, the officer is under a duty to exercise his discretion according to law, the latter that he is under a duty to take whatever active measures may be authorized by the power. In construing a statute conferring a power by permissive or facultative expressions, it is important not to mistake indications or evidences, found in the context or subject matter, of an intention that a right to call for the exercise of the discretion should exist, for indications or evidences of an intention that the officer in whom the power is reposed should be under a duty, upon request and upon fulfilment of the necessary conditions, to do the thing authorized. In the subject matter and context of s. 66 (2) there are few positive considerations to be found in support of the interpretation which makes it obligatory upon the magistrate, once he is satisfied that the statutory nuisance exists, to make an order of one description or another. But there is one consideration which is usually accounted very strong. It is that the power is conferred upon a judicial tribunal and to be invoked by a judicial proceeding. Jurisdiction and powers are conferred on judicial bodies, usually for the enforcement of rights and the protection of interests, and permissive language will often in such a case be used not because it is intended to give the tribunal a discretion to grant or refuse the remedy, but because, although it is intended or contemplated that persons interested will be entitled to the remedy the tribunal is empowered to give, it is also intended, or at all events taken for granted, that the existence of the interest and the validity of the claim to the remedy of a person seeking it will be for the tribunal to determine. It is no more than an instinctive recognition of the truth of Ulpian's dictum - nemo qui condemnare potest, absolvere non potest (Dig. 50: 17: 37). No doubt in the construction of s. 66 (2) the fact that it is a magistrate or justices who are empowered and that the proceeding is by complaint is a consideration of weight. To this may be added the fact that by an amendment made by Act No. 16 of 1944 the magistrate may in addition to making an order impose a penalty.