I'm practicing law right now and I'm just learning about cases like this. When your father receives the FDA Warning Letter, he has 15 days to respond, and it is important not to miss that deadline. The response should be very detailed, with a clear plan of action to correct the violations. About the lawyer: it's best to contact an attorney who specializes in FDA regulation. This may not just be a general medical lawyer, but an expert in FDA compliance. I would recommend checking out the article on this topic at https://www.jdsupra.com/legalnews/did-you-receive-an-fda-warning-letter-9347557/ - it gives a good overview of what to do after receiving such a letter and how to prepare a proper response.