Regarding Resignation

Hi, am asking this question on behalf of my friend.My friend has resigned yesterday to his organization by mentioning that due to some serious family reasons he can not serve the notice period of 90 days and he can serve notice period only for 20 days as its a family issue for him.he has completed 9 months in the organization where 6 months of probation period they have.But he has not yet received the confirmation letter as well.Few days before he has requested for 3 weeks of leaves to resolve his family issue but the company denied and gave him only 1 week of leave. Now he has resigned and the management is threatening him that he has to speak with their lawyer. and they cut the conversation. He doesn't wants to go any legal action as he is already suffering from his family matter. What are his rights in this case because he can not follow the 90 days of notice period. Can somebody please guide me on this. This is really urgent. Really company can take any legal action against him apart from not giving experience letter, final settlement amount or asking payoff option. My name is Tina.