can they make you stop selling your own invention? Can they make you pay them licensing fees for something you designed way before they did? I designed a unique baby outfit in 2008 and started selling it at trade shows and to the public in the same year. I filed a non provisional patent in 2009 but a lawyer advised me not to pursue it as it was costly and most clothing patents were rejected. Wish I had gotten better advice because fast forward to 2017 and I have received a cease and desist letter from someone who invented the same design in 2011 and was granted a utility patent in 2016. They are demanding a licensing fee or for me to stop selling it. I would love to know if I have any legal recourse as I have put a lot of $ and time into developing my patterns and have been growing this line for 8 years.
In short: as long as they have a valid patent, they can do that.
However, if what you say is true then you have a very good position for negotiation.
I strongly advise you to contact a patent lawyer to assist you. If you cannot do that, answer the cease and desist letter with proof that you were selling the product before their patent. But note however that if you understood something wrong or only had a similar product or they don't believe/understand what you are telling them you lost valuable time. (Normally invalidation takes more time then litigation, so time is critical here. - Germany) In the US invalidity can be a good defense against a suit, but it will cost a lot of money to go through a law suit anyways.