Legal, are you selling it as an antique?
First of all, you must clearly understand that your patent should be valid within China,
Secondly , patent transfer can be sold out/exclusive license/exclusive license/general license.
If this patent is sold out, your rights will be transferred, how can you sell it?
If your patent is a general license, you can license it to 1.3 billion people without any problem.
As for your patent being sold to others, if you still want to produce it yourself, it means If you infringe the law, you should accept the court's decision and compensate the other party.