Comparative Contract Law

Introduction

Contract law governs the formation, performance, and enforcement of voluntary agreements. Despite the universality of contractual exchange, legal systems have developed markedly different doctrines to determine which promises are enforceable, how contracts are formed, what duties arise during performance, and what remedies are available for breach. The comparative study of contract law reveals fundamental conceptual differences — particularly between the common law and civil law traditions — alongside significant convergence driven by international trade, harmonization projects, and European integration. The common law of contracts originated in the action of assumpsit and was systematized in the nineteenth century. Civil law contract doctrine is rooted in Roman law and codified in the great civil codes.

Consideration vs. Cause

One of the most fundamental doctrinal differences concerns the basis of contractual obligation. Common law requires consideration: a promise is enforceable only if the promisee gives something in exchange — a benefit to the promisor or a detriment to the promisee. Consideration must be bargained for and must have some value, though courts do not generally inquire into adequacy. The doctrine distinguishes binding promises from gratuitous promises, which are enforceable only if made by deed (under seal). Consideration can be executed (an act done in exchange for a promise) or executory (a promise exchanged for a promise). The requirement has been criticized as technical and has been eroded by promissory estoppel, which enforces promises without consideration where reliance is reasonable and detrimental.

Civil law systems lack a consideration requirement. French law historically required cause (Article 1131 of the Code Civil before the 2016 reforms) — the reason or motive for undertaking the obligation. The cause could be objective (the counter-performance in a bilateral contract) or subjective (the personal motive of the promisor). The 2016 reform of French contract law abolished cause as a distinct requirement, simplifying formation requirements while retaining control over illicit motives through the requirement of a lawful and certain content. German law does not require consideration or cause. Contract formation requires mutual declarations of intent (Willenserklärungen) and, in some cases, delivery of the thing (real contracts). The parties’ serious intention to be bound is sufficient. Abstract promises (abstrakte Schuldversprechen) are enforceable without reference to their underlying reason. The absence of consideration makes civil law more receptive to gratuitous promises and unilateral promises.

Offer and Acceptance

Both systems recognize contract formation through offer and acceptance, but with important differences. In common law, the general rule is that acceptance takes effect when dispatched (the mailbox rule), meaning acceptance is effective upon posting, even if it never arrives. This rule, established in Adams v. Lindsell (1818), allocates the risk of transmission loss to the offeror. The offeror may avoid the rule by requiring receipt. Revocation of an offer is effective when communicated, even if the offer promised to remain open (firm offers are unenforceable without consideration or a seal). In civil law systems, acceptance generally takes effect when received by the offeror (the receipt rule). The offeror bears the risk of loss only after receipt. French law (Article 1121 Code Civil, 2016 reform) provides that acceptance is effective upon receipt; the offer is revocable until received by the offeree, though sudden revocation without a reasonable period may engage the offeror’s delictual liability. German law (Section 130 BGB) clearly follows the receipt rule: a declaration of intent takes effect when it reaches the addressee. German law also recognizes binding firm offers (Section 145 BGB): an offeror is bound by the offer unless they have excluded binding effect. These differences affect cross-border contracting and have been addressed by the CISG, which follows the receipt rule for both offers and acceptances.

Good Faith in Performance

Good faith (bona fides) is a central organizing principle of civil contract law. German law (Section 242 BGB) requires performance in accordance with good faith (Treu und Glauben), a general clause that courts have used to develop duties of disclosure, cooperation, and consideration of the other party’s interests. The duty not to abuse rights, the principle of change of circumstances (Wegfall der Geschäftsgrundlage), and duties of pre-contractual disclosure (culpa in contrahendo) all derive from Section 242. French law traditionally limited good faith to the performance stage but the 2016 reform extended it to contract formation and negotiation (Article 1104 Code Civil). The duty of good faith also governs the abuse of contractual rights and the renegotiation of contracts when circumstances change (imprévision).

Common law has traditionally been hostile to a general duty of good faith. English law rejects an implied duty of good faith in contract performance, preferring specific implied terms and doctrines of estoppel, duress, and misrepresentation to address particular injustices. The general principle is that parties may pursue their self-interest aggressively during both negotiation and performance. American law takes a more receptive approach: the Uniform Commercial Code (Section 1-304) imposes a duty of good faith in the performance and enforcement of every contract within its scope, and the Restatement (Second) of Contracts (Section 205) extends the duty to all contracts. Good faith in U.S. law prohibits evading the spirit of the bargain, failing to cooperate, and exercising discretion arbitrarily. The civil law embrace of good faith reflects a more communitarian conception of contract; the common law reluctance reflects a more individualistic, freedom-of-contract orientation.

Remedies for Breach

The two traditions approach remedies differently. In civil law, specific performance is the primary remedy: the obligee is entitled to actual performance of the promised obligation. French law (Article 1221 Code Civil) allows specific performance unless it is impossible or grossly disproportionate. German law (Section 241 BGB) similarly prioritizes specific performance (Naturalherstellung). Damages are secondary, available if performance is impossible, delayed, or defective. The emphasis on specific performance reflects the civil law view that a contractual obligation creates a binding duty to perform.

Common law treats damages as the primary remedy and specific performance as exceptional, available only when damages are inadequate (the subject matter is unique — land, rare goods, or specific chattels). The preference for damages reflects the common law’s historical development through the action of assumpsit (compensating for harm caused by breach) and the efficiency-oriented view that promisors should be free to breach and pay damages if performance becomes uneconomic (efficient breach theory). Specific performance is discretionary and will not be granted where constant supervision would be required. Liquidated damages clauses are enforceable if they represent a genuine pre-estimate of loss but are unenforceable as penalties if they are extravagant or unconscionable. Civil law systems are more permissive of agreed damages clauses and penalty clauses, subject only to judicial reduction if excessively high.

The CISG

The United Nations Convention on Contracts for the International Sale of Goods (CISG, 1980) is the most successful harmonization instrument in contract law, with over ninety-five parties including all major trading nations. The CISG provides uniform rules for international sales contracts, covering formation, obligations of buyer and seller, risk of loss, and remedies. It adopts a middle path between common law and civil law: it follows the receipt rule for acceptance, requires no consideration, recognizes specific performance but allows courts to refuse it if they would not do so under domestic law, and imposes a duty of good faith only in interpretation (Article 7(1)), not as a positive duty on performance. The CISG excludes consumer sales, certain types of goods, and issues of validity. Its success has inspired other harmonization projects. The UNIDROIT Principles of International Commercial Contracts (2016) provide a restatement of general contract law principles applicable to international contracts. The Principles of European Contract Law (PECL, 2003) similarly provide a model for European contract law.

The Draft Common Frame of Reference

The Draft Common Frame of Reference (DCFR, 2009) is an academic project of the Study Group on a European Civil Code and the Research Group on Existing EC Private Law (Acquis Group). The DCFR proposes comprehensive rules for European private law, including contract, tort, property, and unjust enrichment. Its contract law provisions build on the PECL and reflect comparative analysis of European legal systems. The DCFR adopts civil law positions on some issues (good faith as a fundamental principle, specific performance as the primary remedy) and common law positions on others. It has influenced EU legislation and Court of Justice jurisprudence but remains an academic text rather than binding law. The DCFR represents the most ambitious attempt at European-wide contract law harmonization, though political support for a European Civil Code has waned.