There is no single law that governs how insurance companies are required to behave. In 1945, the McCarran-Ferguson Act (Federal) was approved by Congress to essentially disallow any regulation of the insurance industry on a federal level. The states themselves have individual insurance watch-groups and agencies that oversee the practices of insurance companies within their state, but these do vary state to state. Generally, these "unfair insurance practices acts" outlaw all of the things deemed to be in "bad faith", such as neglecting to pay a claim, non-communication and delay of claim payment. You can search the web or local library for your specific state's laws.