appearance of Common law forbearance.70 The same approach is taken in Austrian law.71

Lapse of time may lead to loss of a right even before the relevant period of prescription has expired, based upon Verwirkung.72 This is controversial, as it seems to undermine the clear policy of the rules on prescription.

6.  Model Law and renunciations of rights

The PECL do not specifically deal with renunciations of contractual rights, so there is no reason why such a release should not be seen as either con­ tractual or promissory in nature, depending on the circumstances. The DCFR also does not specifically regulate renunciations, though Article III.-1:108 provides permissively that the variation or termination of a right, obligation or contract can occur ‘by agreement’ at any time. That statement need not be seen as prohibiting unilateral renunciations, how­ ever, and the general legal recognition in the DCFR of unilateral under­ takings73 seems quite capable of applying to a unilateral renunciation of contractual rights, either in the form of a unilateral promise to release or simply an immediate unilateral release.

Article 5.1.9(1) of the Unidroit Principles of International Commercial Contracts provides a contractual model for release by the creditor of its right against the debtor (such release requiring to be ‘by agreement’). This naturally presupposes the usual methods for conclu­ sion of such a contract, typically offer and acceptance. However, if the offer of release is a gratuitous one, then acceptance of it is deemed to have been made unless the obligor rejects the offer without delay once becom­ ing aware of it.74 No clear justification is available for the fictional consent approach of this provision, but it has been observed that a convincing rationale may be that, because a gratuitous release confers only benefits upon the creditor but no duties, there is no reason not to imply consent

70See further Markesinis et al., German Law of Contract, p. 123.

71In Austria, the Court of the Federal Chamber of Commerce and Industry has allowed the defence of Verwirkung, based on the gap-filling principle of good faith, to assist a buyer who did not (as required under the contract) give timely notice of defects, because the seller at first did not insist upon such timely notice and had begun to renegotiate the contract (see Schlechtriem, ‘Good Faith in German Law and in International Uniform Laws’). This approach, note, is based on good faith rather than promise.

72See discussion of the subject in Vaquer, ‘Verwirkung versus Laches’.

73 See Art. II.-1:103(2).    74  Art. 5.1.9(2).