is it legal to inform a retailer that you will no longer sell your product to them if they do not desist in selling another company's product that your company feels that it's an inferior reproduction of your original product (that you proved in a billion dollar lawsuit)?
It depends if your not selling the product would be a breach of contract. Do you have an agreement with them to sell them the product for a specific time and other such terms?
And if you won a billion dollar lawsuit, congratulations!
Child Custody Lawyer
Take some of your billion dollar award and hire an attorney.
DISCLAIMER: This answer is provided as general information, which may not be appropriate for the specific facts of your particular situation. No attorney-client relationship has been established based on this limited communication. You are advised to consult with an attorney in your jurisdiction before taking any action or inaction that may affect your legal rights. www.hecklerlawoffice.com
You may have rights under breach of contract. You may have rights under "antitrust" laws. Your facts will be critical. when you say you prevailed in a "billion dollar lawsuit" you make lawyers wonder about your honesty, why a "billionaire" would be asking for free advice on Avvo, and I know of no cause of action where the out come is "Judgement for plaintiff/defendant based on the grounds of inferior product".
The above is general legal and business analysis. It is not "legal advise" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.
Intellectual Property Law Attorney
I am reading your question to mean that you have two suppliers, one that makes an allegedly "original" product and one that makes an alleged "knock off" product. Apparently the OEM claims to have won a major lawsuit against the imitator, and now is telling you to cut off the imitator or risk loss of the OEM product supply.
Not knowing anything else beyond your question, when your OEM refuses to sell to you, unless you do something, this is a classic case of "refusal to deal." Sometimes refusal to deal is ok under anti-trust laws - for example, in case you might have stiffed your supplier on a few invoices. Other times, refusal to deal establishes anti-trust liability - for example, in case the refusal is used as leverage to get a competitor out of the market, this often will be viewed by the courts as "unfair" competition.
Consult an anti-trust attorney.
You are not my client. I am not your attorney. The above comments are not confidential, not "legal advice", and not "legal opinion". I am licensed as a patent attorney and in the State of Connecticut. Retain and consult an appropriately licensed attorney to identify the laws and facts material to your concerns.