The chief problems in the enforcement by injunction of negative promises arise where the negative promise is only part of an outstanding bilateral contract consisting of dependent promises, not all of which are specifically enforceable - as notably where they are personal in their nature. In 1852 Lord St. Leonards decided the case of Lumley v. Wagner,47 which has subsequently been the leading authority for an extension of the right to enforce such negative promises, especially in contracts of personal service, but also in other contracts. The defendant in that case had agreed to sing at the plaintiff's theatre, from the first of April to the first of July following the date of the contract. She further contracted not to sing elsewhere during that period. The court, though professing inability to enforce the whole contract specifically, granted an injunction, restraining her from singing elsewhere. It is obvious that this decision violates two principles which have been generally supposed to be rules of equity: -
(1) That specific performance of part of a defendant's obligation will not be granted, leaving outstanding further connected obligations to the plaintiff for which the only remedy would be an action for damages.48
(2) The rule of mutuality; since the defendant is compelled to performs material part of her promise, when her only redress if the plaintiff fails to perform on his part will be an action for damages.
45 American, etc., Co. v. Crossman, 57 Fed. 1021; Kinsman v. Parkhurst, 18 How. 289, 15 L. Ed. 385.
46 Dietrichsen v. Cabburn, 2 Phillips, 52; Donnell v. Bennett, 22 Ch. D. 835. See also Metropolitan Electric Supply Co. v. Ginder,  2 Ch. 799; Cf. Fothergill v. Rowland, L. K. 17 Eq. 132, stated in the preceding section, n. 38.
47 1 De G. M. & G. 604.
48 See supra, Sec. 1430. It is expressly assumed by Lord St. Leonards that the plaintiff might bring an action for damages for the defendant's failure to sing at his theatre. The case does not come within the recognised exceptions to the requirement of complete enforcement discussed in a preceding section (Sec. 1431). Had the plaintiff bought of the defendant a record of her voice, a covenant on her part not to sing in the future, given in order to enhance the value of the record, would have afforded a clear basis for relief, but the decision cannot be thus explained.
More specifically, the case is inconsistent with several earlier decisions denying a plaintiff an injunction to enforce a negative covenant where the court was unable to enforce specifically a correlative affirmative undertaking.49 For this reason, the decision has been frequently criticized, but it has nevertheless been followed both in England,50 and in the United States;51 but what the boundaries are of the principle for which it stands has been the subject of dispute. The contract in question was one of service; the service was of an expert and peculiar character; there was an express negative covenant and though the defendant's entire performance was not, this particular covenant was fully enforced by the injunction; performance of this negative covenant was of value to the plaintiff apart from its correlative affirmative, since competition would thereby be limited. Which of these circumstances are essential for the jurisdiction?