A contract, as a general rule, creates rights and obligations only between the parties who actually entered into it. This is the doctrine of privity of contract: a person who is not a party to a contract cannot sue to enforce it, and cannot be sued upon it, even where the contract was expressly made for that person's benefit. The rule applies regardless of how directly a third person may be affected by a contract's performance or breach; being the intended beneficiary of a promise is not, by itself, enough to give that person any right to enforce the promise in their own name.

The doctrine follows from a closely related principle: consideration must move from the promisee. A person seeking to enforce a promise must generally show that they themselves furnished something of value in exchange for it. A third party who supplied no consideration of their own, even if a contracting party furnished consideration specifically intended to benefit them, generally has no independent right to sue on the resulting promise.

The rule of privity, however, is subject to several well-recognised exceptions, each addressing a situation where strict application of the rule would produce an unjust result. First, where a contract creates a trust in favour of a third person -- that is, where one contracting party holds a right or benefit under the contract on trust for a named beneficiary -- that beneficiary may enforce the trust directly, even though they were never a party to the contract that created it. Second, where a contract is made by an agent on behalf of a principal, the principal may sue and be sued on the contract, even though the principal did not personally sign it, because the agent acted throughout as the principal's own representative. Third, in the case of a family arrangement or marriage settlement, courts have permitted a family member who was not a party to the arrangement, but who takes a direct benefit under it, to enforce that benefit. Fourth, where a contract creates a charge on a specific, identified fund in favour of a named third person, that person may enforce their right to be paid from the charged fund, even without being a party to the agreement that created the charge.

Where none of these recognised exceptions applies, a third party's remedy, if any, lies not against the party who broke the promise, but against the contracting party who was supposed to secure that benefit for them in the first place, on whatever separate ground of law the facts happen to support -- and not on the original contract itself, to which the third party never was, and remains, a stranger.