"The final questions, then, are whether the Supreme Court had a discretion to refuse an injunction to restrain a breach of the negative covenant and, if so, whether in the circumstances of this case the Court should have exercised its discretion against the applicant.
Lord Cairns LC in Doherty v Allman said that a court of equity has no discretion to exercise when an injunction is sought to enforce a negative covenant in a contract. His Lordship drew a distinction between 'a negative covenant' and a covenant which is affirmative only. The distinction so drawn was, I think, not one deriving from the language or form in which a covenant happened to be expressed, but one arising from the substance of the obligation imposed by the covenant (see, eg, Wolverhampton and Walsall Railway Co v London and North-Western Railway Co (1873) 16 Eq 433 at 440, per Lord Selborne LC).
There has been general agreement that Lord Cairns' statement that a court of equity has no discretion to refuse an injunction restraining a breach of a negative covenant is not accurate. In Doherty v Allman itself Lord Blackburn, who, like Lord Selborne LC in the Wolverhampton Case, was inclined to repudiate the notion that a distinction should be made between negative and affirmative words, considered that there were cases in which a court of equity would refuse to enforce a negative covenant on discretionary grounds.
However, there has been general disagreement as to how Lord Cairns' statement should be reformed if it is to accurately express the true principle. The reason for this is that it is quite impossible to formulate an illuminating statement of principle which is capable of universal application. There is no limit to the number and to the kind of negative stipulations, express or implied, which the courts may be asked to enforce. It is not surprising, therefore, that it has emerged from a long line of judicial decisions that the attitudes of the courts to the enforcement of negative stipulations have varied according to the nature of the stipulation, the nature of the contract in which it is found, the effect which enforcement will have on the relationship of the parties under the contract and the character of the order required to enforce the stipulation. "