Legal Question in Civil Litigation in Minnesota

Interesting question. No, selling the dog would not make the agreement null and void unless there is language in the agreement that expresses it. So the boyfriend just can't sell the dog to you, your daughter or anyone else and make the agreement go away. Generally, courts just deal with money and don't deal with specific performance (e.g. making a dog owner allow visitation to a previous owner). I have no idea what a judge would do in your situation, but she probably wouldn't be happy that this case was in her court. I am not sure what you mean by "legal document." There is nothing in your question that makes it appear that it is an "illegal document." Legally binding agreements don't even have to be written.