An unenforceable contract or transaction's one that's valid, but which the court won't enforce. Unenforceable's usually used in contradistinction to void (or void ab initio) and voidable. If the parties perform the agreement, it'll be valid, but the court won't compel them if they don't. An example of a transaction which's an unenforceable contract's a contract for prostitution under English law. Prostitution isn't actually a crime under English law, although both soliciting a prostitute and li… (More on Unenforceable)