R2d § 317
Assignment of a Right
(1) An assignment of a right is a manifestation of the assignor's intention to transfer it by virtue of which the assignor's right to performance by the obligor is extinguished in whole or in part and the assignee acquires a right to such performance. (2) A contractual right can be assigned unless (a) the substitution of a right of the assignee for the right of the assignor would materially change the duty of the obligor, or materially increase the burden or risk imposed on him by his contract, or materially impair his chance of obtaining return performance, or materially reduce its value to him, or (b) the assignment is forbidden by statute or is otherwise inoperative on grounds of public policy, or (c) assignment is validly precluded by contract.
Professor's notes
Two-part rule. (1) Mechanics of assignment: the assignor manifests intent to transfer; the assignor's right against the obligor is extinguished; the assignee acquires the right. (2) Limits on assignability: rights can be assigned UNLESS one of three blockers applies: (a) material change in the obligor's duty, burden, risk, or return value; (b) statutory or public-policy bar; (c) a valid contractual anti-assignment clause.
Birdsall v. Saucier operationalizes the materiality limit: an obligor cannot avoid an assignment simply by preferring the original obligee, but can defeat it where substitution would meaningfully change what was bargained for.
Common misunderstanding: students think anti-assignment clauses are absolute. Section 322 (and modern decisions) read most boilerplate anti-assignment clauses to bar delegation of duties, not the assignment of receivables. The distinction matters because most commercial assignments are receivables. Pair § 317 with § 318 (delegation) and § 322 (anti-assignment clauses) for the full picture.
Cases that operationalize this rule
The default rule favors assignability. The exceptions are narrow and fact-specific.