A learned writer has thus summarized the results of the decisions: 72
"Much of the difficulty in such cases grows out of confusing situations where a court ought not to enforce a covenant directly or indirectly and those where there is no reason why it should not be enforced if it may be, but there are practical considerations in the way of direct enforcement. Where the covenant calls for 'service of a confining nature and under the direction of the employer as to details,'73 there is more than a practical obstacle. The court ought not to exact performance even if it could. In other cases the interference with privacy or personal liberty may make direct enforcement impossible. In others it may be impossible to coerce directly a course of affirmative action involving individual taste or skill or judgment. In such cases there may be no policy of the law against enforcing the service, so that if the court, without making over the contract, can make use of a negative of separate significance to enforce the contract 'in the only manner in which it could be enforced,'74 there may be every reason for doing so. Where breach of the negative involves a damage by itself apart from or over and above breach of the affirmative, it can be no objection to enforcement of that negative that it may tend to enforce an affirmative that ought to be performed. Mutuality of performance is a doctrine of equity for the protection of defendants by insuring to them when performance is exacted of them that they get the counter performance due them. If they obstinately refuse to avail themselves of the opportunity to have all that the contract calls for, by remaining idle when enjoined from breaking the negative covenant, they ought not to be heard to complain. Great hardship upon the plaintiff,75 may properly move the court to attach little weight to the possibility that the defendant, by doing nothing, may perform part of the contract with no equivalent."
This negative promise was enforced by injunction. To the same effect are Peerless Pattern Go. v. Gaunt-lett Dry Goods Co., 171 Mich. 168, 136 N. W. 1113, 42 L. R. A. (N. 8.) 843; Standard Fashion Co. v. Siegei-Cooper Co., 30 N. Y. App. D. 564, 52 N. Y. S. 433, 157 N. Y. 60, 51 N. E. 408, 43 L. R. A. 854, 68 Am. St Rep. 749; Butterick Publishing Co. v. Rose, 141 Wis. 533, 124 N. W. 647. But cf. Standard Fashion Co. 9. Magrane-Houston Co., 251 Fed.
559, 163 C. C. A. 553, 259 Fed. 793 (C. C. A.).
72 Roscoe Pound, 33 Harv. Law Rev. 439.
73 Citing Clyatt v. United States, 197 N. S. 207, 215.
74 Citing Yorkshire Miners' Ass'n v. Howden,  A. C. 256, 269. See also Cincinnati v. Marsans, 216 Fed. 269, Metropolitan Exhibition Co. v. Ewing, 42 Fed. 198; Great Northern R. Co. v. Telephone Co., 27 N. D. 256, 265, 145 N. W. 1062.