The US Constitution puts the individual states in charge of commerce inside their various borders.  Insurance is a type of commerce, so each state has its own insurance regulations. These regulations apply to every insurance company, agent, adjuster and employee in the state. This includes all types of insurance: auto, life, health, homeowners and business. If your insurance company is not treating you right, there is a place you can complain where they will actually do something about it.
National Association of Insurance Commissioners, or NAIC
The citizens of each state elect a state insurance commissioner. This elected official is charged with making the insurance rules in her state. She also is expected to enforce these rules. She has a state department of insurance full of hundreds or thousands of employees to help her. All the insurance commissioners of all the different states have formed a commission to help them, too. The National Association of Insurance Commissioners (NAIC) website is a resource where insurance customers can find information on all the different state departments of insurance (DOIs). 
Send Your Insurance Complaints to Your State Department of Insurance (DOI)
Use the NAIC website link at the bottom of this page to find contact information for your state’s department of insurance (DOI). Send a written complaint to your DOI if any insurance company, agent, adjuster or employee breaks a promise to you or does anything unethical. Insurance companies have to be licensed in your state in order to do business. Your DOI is the agency which licenses your insurance company. Your insurance company will listen to the DOI. It can fine companies for not following its regulations. If they behave really badly the DOI can take away their license to do business.
During the eight years I adjusted claims for Farmers Insurance, I witnessed first hand how DOI complaints receive top priority. The supervisor places them in the center of the adjuster’s desk first thing in the morning and follows up to make sure they have been handled before lunch. Each adjuster has 50 to 100 claims he or she is handling at any given time, so this is a big deal.
Video: The NAIC stands firm in protecting life insurance and annuity owners.
Mark Wahlstrom explains how the state insurance commissioners intercede on behalf of insurance customers.
References and Resources
 US Constitution Section 8 – Powers of Congress says Congress regulates commerce with foreign countries and among the different states. Since commerce within each state is not mentioned, it falls under the regulation of each individual state per the 10th amendment.
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