This section is from the book "The Law Of Contracts", by William Herbert Page. Also available from Amazon: Commercial Contracts: A Practical Guide to Deals, Contracts, Agreements and Promises.
Waiver is therefore a consequence of certain acts or omissions. It is the abandonment or renunciation of a right, and since this abandonment or renunciation may be made in a number of ways, the use of the term waiver indicates the result which is reached, but does not indicate the means by which the result is reached.
It is frequently said that a new contract operates as a waiver of rights under the original contract. The new contract has already been discussed,10 and for that reason waiver which is the result of a new contract will not be treated in this connection. It is sufficient to point out that in cases in which it is claimed that waiver arises by reason of a new contract, the party who makes such claim must be able to show the existence of a new contract, including a sufficient consideration, in most jurisdictions.11
In cases of election, one of the parties has a choice between two rights, but the law denies to him the right to take both. If he takes one as a finality, this operates as a renunciation of his alternative right to take the other which he once possessed. The giving up of such alternative right is very frequently called a waiver. While this use of the term has been criticized severely,12 the fact remains that before the election was made, the party had his choice between two inconsistent rights, and after the final election is made, his choice of one right prevents him from asserting the other right, even if he wishes to surrender the right which he has elected and to assert the right which he had not elected. Some term is necessary to indicate the finality of his renunciation of the right which he does not elect, as well as the finality of his election of the right which he elects. In spite of the objection which is made to the use of the term waiver in this connection, it seems to be a useful term, and one which has the authority of the courts. The practical trouble in its use, as in the use of other terms, which indicate results and consequences, is that the courts occasionally use the term waiver in this connection without pointing out clearly the inconsistent rights between which the party could elect, and the acts which are relied upon to show his election of one and his waiver of the other.
10 See Sec. 2457 et seq.
11 See Sec. 2461.
For the theory that consideration is not necessary in such cases, see Sec. 2465.
Cases of this sort are not really causes of waiver, but new contract, unless the courts are ready to say that certain forms of simple contract do not need consideration. If the result of treating the rights under the former contract as waived is correct, it should be justified in some other way, as by explaining the cases on the theory of election or estoppel, or by recognizing the existence of a type of waiver which does not arise in any of these ways. See Sec. 2664.
The term waiver is frequently used to indicate the result of estoppel. A party may have a right to which he is originally entitled and which he may assert; but by his words or acts he may have induced the adversary party so to act in reliance thereon that the adversary party will be prejudiced seriously if such original right can be asserted. Accordingly, the original right is lost and this loss of such right is frequently called waiver. A serious objection to the use of waiver in this connection is that the party against whom the estoppel operates frequently has no intention of estopping himself by his words or his acts from asserting his original right. The estoppel is imposed by law for the purpose of justice without any regard to the actual intention of the party who is estopped and frequently in defiance of his intention as the only available means of preventing him from securing some unfair advantage by a reliance upon technical legal rights. For these reasons the use of waiver in connection with estoppel seems less desirable than its use in connection with election. It is true, however, that even in election the party who makes the election may not know that he is bound to choose between his rights and his final renunciation of one of such rights, but his election of the other is frequently due to the application of rules of law without any regard to his actual intention. At the same time the nature of the case is such that in the greater number of cases of election the party to whom such right of election is given by law must know that he can not claim both rights at once. In the law of contracts especially, he must know that if he claims under the contract, he can not at the same time claim against it.
12 Waiver Distributed, by John S. Ewart, 7.
After all the cases in which rights arising under a contract are discharged by waiver, which can possibly be explained by the theory of the new contract or election or estoppel are thus explained, there nevertheless remain a large number of cases in which we must either say that the law has given effect to the voluntary and intentional renunciation of a right, or else we make use of severe and heroic means of bringing such case under the general class of the new contract or of election. In many of the cases the theory of the new contract can be invoked only if we are ready to enforce contracts without consideration. In many of the cases, the theory of election can be invoked only if we are ready to say that the party may elect between claiming his right or his defense and giving it up; and since election means a choice between two inconsistent rights, it seems lite a perversion of terms to use it as indicating a choice between the assertion and the renunciation of a right. Many of the cases in which" the doctrine of waiver is invoked by the courts can be explained on the theory of estoppel only if we are ready to base estoppel upon the promises for the future as well as representation of existing or past facts. Estoppel ordinarily imports an erroneous statement as to facts either present or past If future promises, in reliance upon which the adversary party has acted, are to be treated as enforceable on the theory of estoppel, consideration in the technical sense is unnecessary where-ever any action has been taken in reliance upon such promise, and accordingly the rule that the consideration must be that which is contemplated by the agreement of the parties,13 can never apply to render the contract unenforceable, since the doctrine of estoppel will make the promise enforceable in such cases.14