7) Defences

The four main defences to an action in private nuisance are statutory authorization, statutory immunity, consent, and prescription.

a) Statutory Authority

The defence of statutory authority was established in the nineteenth century to protect legislatively approved public and private enterprises and activities that were in the public interest and for the public good. The authorizing legislation itself rarely spoke clearly on the issue of tortious liability arising from the activity, but judicial policy favoured protecting fledgling industries, municipalities, public utilities, and other undertakings approved of by the legislature. In the twentieth century, judicial attitudes changed and there is now less enthusiasm for policies that shelter legislatively approved activities from tortious liability. There is much greater support for the view that the loss caused by a beneficial and authorized enterprise should be allocated to the enterprise so that the loss may ultimately be spread among the community that benefits from it, rather than to private persons or businesses who are often less able to spread the loss.

The Supreme Court re-examined the scope of the defence in two cases, Tock v. St. John's (City) Metropolitan Area Board [Note 37: Above note 4.] and Ryan v. Victoria (City of). [Note 38: [1999] 1 S.C.R. 201.] Tock contains an extensive but inconclusive discussion of the defence. Ryan rather tersely brings some certainty to the issue. In Tock the basement of the plaintiff's house was flooded when the defendant municipality's storm sewer became blocked in the course of a heavy rainfall. The storm sewer was constructed and maintained under statutory authority. The Court agreed that the defence of statutory authority must be construed narrowly but there was no agreement on the appropriate principles to achieve this. Wilson J. sought to largely negate the defence by confining it to statutory authority that gave no discretion to the defendant as to the time, location, or performance of the authorized activity. Since almost all modern legislation is discretionary in respect of the performance of the activity, the defence would be largely inapplicable. If the defence was prima facie applicable, the defendant carried the further burden of proving that the nuisance was inevitable in spite of every reasonable step being taken to avoid it. LaForest J. called for an open consideration of who should bear the loss. All the surrounding circumstances, including the utility of the authorized conduct, the degree of interference with private rights, and the availability and cost of preventive measures must be considered, but, as a general rule, it is reasonable to allocate material damage resulting from isolated and infrequent occurrences to defendants, and ordinary and diffuse disturbances to reasonable comfort to plaintiffs. Sopinka J. held to the more conventional view that the defence applied to all authorized activities but the defence was not made out unless it was established that the nuisance was an inevitable consequence of the activity. Each of these approaches led to the conclusion that the defence was inapplicable in Tock but no judge was able to command a majority of the Court in support of his or her judgment.

A period of uncertainty followed Tock, which was finally resolved by the unanimous decision of the Court in Ryan. Ryan was a case of public nuisance, dealing with railway tracks running down the centre of a city street. The tracks were dangerous because the flangeway gap running along the inside edge of the tracks was wide enough to trap the tires of motorcycles, thereby creating a risk of accidents of the kind suffered by the plaintiff. The defendant railway company argued that it was not liable because the railway track was statutorily authorized and it had complied with all rules and regulations in respect of it. The Court held that the tracks were a public nuisance and, on the facts, the statutory authorization was no defence. It summarily repudiated the approaches of Wilson and LaForest JJ. and endorsed the judgment of Sopinka J. In its view, to establish the defence of statutory authority, the defendant must prove that it was practically impossible to avoid creating a nuisance. It is not sufficient to show that reasonable care has been taken. The nuisance must be shown to be an inevitable and unavoidable result of the authorized activity. Since the flangeway gap could have been narrowed to prevent the accident, the defence failed.

b) Statutory Immunity

It is ironic that, at a time when the defence of statutory authority is receiving a narrow interpretation, some provincial legislatures have selected certain beneficial land uses for complete immunity from the tort of private nuisance. This legislation has been prompted largely by the conflict between agricultural operations in rural areas and expanding urban communities, new residential developments in rural areas, hobby farms, and cottage developments. The first Act of this kind was The Nuisance Act [Note 39: R.S.M. 1987, c. N120.] of Manitoba. The Act was passed in response to a successful action against a hog producer in respect of the odour produced by his operation. The plaintiff, who owned a nearby residential property, secured an injunction and an award of damages. The government of the day disapproved of the decision and sought to prohibit the private nuisance action from being used in this manner by passage of The Nuisance Act. [Note 40: It is interesting that legislation was deemed necessary in light of the fact that Canadian judges have, on the whole, been sympathetic to farming interests. There is even some authority suggesting that proof that the nuisance arose from a normal act of animal husbandry is a complete defence: see J. Irvine, "Case Comment: Metson v. R.W. DeWolfe Ltd.; The Changing Face of Nuisance, and Rylands v. Fletcher" (1980), 14 C.C.L.T. 225.] It protects all businesses (including urban operations) from liability in nuisance for odour unless the plaintiff can prove a breach of provincial land-use control statutes and regulations. This legislation was followed ten years later by The Farm Practices Protection Act, [Note 41: S.M. 1992, c. 41. Ontario and British Columbia have similar legislation: see Ontario Farming and Food Production Act, 1998, S.O. 1998, c. 1, s. 2; and British Columbia Farm Practices Protection (Right to Farm) Act, R.S.B.C., 1996, c. 131, s. 2.] which singles out agricultural operations for a broader protection than that provided by the Nuisance Act. An agricultural operation that complies with normal farm practices and legislative land-use control laws cannot be held liable in nuisance for any odour, dust, dirt, smoke, or any similar disturbance. The Act also established a Farm Practices Protection Board with dispute settlement and enforcement functions in respect of abnormal or illegal land use. The action for private nuisance is restricted to situations where the agricultural activity is not protected by the legislation and the bureaucratic settlement procedures have been unsuccessful in resolving the dispute. It may be noted that the Act does not extend to nuisances such as fire, flood, or the drift of agricultural chemicals that cause physical damage to property.

c) Consent

The defence of consent arises infrequently in cases of nuisance. It is sometimes referred to as the defence of consent and acquiescence, but if the latter term suggests that tacit approval by standing by in the face of a nuisance is sufficient to establish the defence, it would be misleading. It appears that there must be strong evidence of approval or active encouragement of the defendant's nuisance-generating activity.

d) Prescription

A privilege to commit a nuisance may in some provinces be acquired by prescription. The defendant must establish that the nuisance (not merely the activity) has continued, uninterrupted, for twenty years, that the plaintiff has known of the nuisance for that period of time, and that the plaintiff has not sued on it or taken any other steps to prevent it. [Note 42: These privileges are known as easements. The technicalities involved in their acquisition are best left to texts on real property.]

e) Contributory Negligence

Contributory negligence does not feature in most private nuisance cases. The plaintiff is, normally, not in a position to move away or avoid the nuisance and the courts have not required plaintiffs to take steps such as building protective structures, keeping windows closed, or taking other measures to mitigate the consequences of the defendant's action. Furthermore, it is no defence that the plaintiff came to the nuisance. In the rare instances where the plaintiff is found guilty of contributory negligence, there may be some apportionment of damages if the language of the applicable contributory negligence legislation permits it.