Thats BS. One state may not impede trade across state lines. If Ohio wishes to regulate policies sold on Ohio then yes it is protected by the 10th. But the 10th does not prevent an Ohioan from buying insurance in Indiana.
Allow me to clarify. Each state regulates the sale of all insurance in its state, whether Life and Health, P&C, etc. Life insurance can be sold to people of other states, provided the agent is licensed in the state in which it is sold.
Health insurance is peculiar because state laws around what constitutes a valid policy vary, sometimes greatly.
Generally speaking, life insurance is fairly consistent across all 50 states, with only a few having different applications, as well as not having reciprocity with other states. NY and CA agent licensing is a nightmare.