I was an auto insurance actuary in a different life. Most states do NOT ban the use of credit in auto insurance pricing, but there are some exceptions. My company actually decided not to do business in California because we could not use credit as a factor. The difference in premium due to credit could often be as high as 12x between the highest and lowest groups.

Some states (Maryland comes to mind) do limit the maximum surcharges you can implement because of credit, although there are sneaky ways around this that everyone uses, like underwriting tiers (GEICO) or using credit in multiple places (Progressive).