It is everywhere agreed that in order to be valid a promise imposing a restraint in trade or occupation must be reasonable. The question of reasonableless is for the court, not the jury;43 and in considering what is reasonable, regard must be paid to
40 Mitchel v. Reynolds, 1 Peere Wms. 181, 190.
41See infra, Sec.1641, n. 75. The general rule most frequently quoted in England and America is laid down in Horner v. Graves, 7 Bing. 735, 743. "We do not see how a better test can be applied to the question whether reasonable or not, than by considering whether the restraint is such only as to afford a fair protection to the interests of the party in favour of whom it is given, and not so large as to interfere with the interests of the public. Whatever restraint is larger than the necessary protection of the party, can be of no benefit to either, it can only be oppressive; and if oppressive, it is, in the eye of the law, unreasonable. Whatever is injurious to the interests of the public is void, on the grounds of public policy."
42 Hall Mfg. Co. v. Western Steel & Iron Works, 227 Fed. 588, 142 C. C. A. 220, L. R. A. 1916 C. 620.
(a) the question whether the promise is wider than is necessary for the protection of the covenantee in some legitimate interest,
(b) the effect of the pronpse upon the covenantee and, (c) the effect upon the public. If the restraint imposed is greater than is necessary for the protection of the covenantee, the promise is necessarily invalid. One whose business is confined to York is not helped by the promise of another not to do business in London, and if the promise is enforced by injunction the promisor is injured, while the promisee is not correspondingly helped. Such a case in the simple form supposed would not often arise, but very commonly a promise is exacted which includes not only a restriction advantageous to the promisee, but one injurious to the promisor without corresponding benefit to the promisee. Such a promise unless divisible,44 is wholly invalid. Even if no objection can be taken on this ground, the effect may conceivably be so harsh in its effects upon the promisor that enforcement of the promise will be refused. Finally, even though neither of the foregoing objections exist, the effect of the promise on the public interest may be such as to make enforcement contrary to public policy. In considering the nature of this last objection, it must be recognized at the outset that the purpose of any restrictive covenant is almost always to lessen competition with the promisee, thereby enabling him to do a larger business and on terms more favorable to himself than he could do if he had not obtained the promise in question. This general purpose has been regarded, especially in America, as so inimical to the public interest that it is only in cases where the restrictive promise is ancillary to some other transaction that its validity has been upheld.45 Thus if a dealer should pay a competitor to promise to go out of business, or cease to compete, the agreement would be invalid.46 But if the same promise were part of a transaction by which the competitor's business was bought, the promise would be valid, unless tending to a dangerous monopoly.47 The policy of allowing the owner of property to sell it on such terms as to secure to the buyer the value of the property must here be balanced against the policy opposing restrictions of competition. A rule of the early decisions, still operative, that consideration must be given for a restrictive promise, even though it is under seal,48 accords with the broader principle that the restrictive promise must be ancillary to some permissible transaction. Moreover, what is often the only effective redress for breach of such a promise- an injunction - may be denied if the consideration is grossly inadequate.460
43 Dowden v. Pook,  1K. B. 46; linn v. Sigsbee, 67 11I. 75; Knight, etc., Co. v. Miller, 172 Ind. 27, 87 N. E. 823; Geiger v. Cawley, 146 Mich. 550, 109 N. W. 1064.
44 See infra, Sec. 1659.
45 See the following section, also, e. g., Harris v. Theus, 149 Ala. 133, 43 So. 131, 10 L. R. A. (N. S.) 204, 123
Am. St. Rep. 17; Kochenrath v. Christ-man, 180 Ky. 799, 203 S. W. 738; Clark v. Needham, 125 Mich. 84, 83 N. W. 1027, 51 L. R. A. 785,84 Am. St. Rep. 559; Euston v. Edgar, 207 Mo. 287,105 S. W. 773; Wood v. Whitehead Bros. Co., 165 N. Y. 545, 59 N. E. 357; Harbinson-Walker Refractories Co. v. Stanton, 227 Pa. 55, 75 Atl. 968.