Independent Sales Rep firing

What is the name of your state?AZ
The company that I have been representing for 8 years now has told me that I need to drop another companies line if I want to continue to do business with them. The company is based in California and from what I've been told they cannot legally tell me to drop any other companies that I work for since we have nothing in writing stating that I cannot work for other companies and this has not been their policy in the past. I am an Independent contractor and am not an employee of the company. They have told me in an email that if I do not quit working for the other company they will terminate me today. This has nothing to do with my performance as all they have stated is that they don't want me working for the other company. Do I have a case here? Thanks.

I'm not aware of any law that prohibits them from terming your services if you refuse to drop the line of a competing company. So no, I don't think you do have a case and I think you were told wrong.

The company is based in California and from what I've been told they cannot legally tell me to drop any other companies that I work for since we have nothing in writing stating that I cannot work for other companies and this has not been their policy in the past. That works both ways. You have nothing in writing stating that they can't end their business relationship with you anytime they feel like it either.

No, you don't have a case. Since there is no contract in place, either party (you or this company) can walk away any time you feel like it. If they want to require you to drop this other company, they can. If you want to refuse, you can. If they want to cancel their business relationship with you, they can do that too.