Under what circumstances can a noncompete agreement be unenforceable?
In the United States, unenforceability is determined if any or all parts of a noncompete clause or contract is found to be "an unfair restraint on trade" (West's Encyclopedia of American Law).
Some states use a "blue pencil doctrine of severability" whereby individual lines of a non-compete clause or contract are subject to rules of enforceability. These states may thus determine individuals items in a contract to be unenforceable. Other states find that if any part is unenforceable, then the whole noncompete clause or contract is unenforceable.