Contract law is generally subject to the common law of States, and although general contract law is common throughout the country, some specific judicial interpretations of a particular element of the treaty may vary from State to State. Mutual promises are a good consideration for maintaining an agreement. [Operations Mgmt. Int`l, Inc.c. Tengasco, Inc., 35 F. Supp. 2d 1052 (E.D. Tenn. 1999)]. This is another apparent exception to the reciprocity rule. Since the obligation to do one`s best is implied and enforceable, both parties are bound by the agreement and there is reciprocity of consideration.
Another exception is that partial payment of the debt by a third party in exchange for a promise to relieve the creditor of the entire amount prevents the creditor from suing the debtor for full payment (see Welby v. Drake).