experience letter not being issued

My known has worked at an IT company in Noida for 6 years. During this job tenure from a programmer he has gained the position of Project Manager. Since he started his own company he left that company in the year 2009 without fully serving the notice period and taking any documentation at that time. His business accrued losses and he again has to look for job.He approached this company again and they were interested in taking him back but at a position of a software devloper. He.He got an offer from another company of a Project Manager. He took that job of Project Manager because of the designation. Now when he wants to settle his accounts with the old company they are refusing to furnish any documents for him. Kindly advise as what can be done in this matter. As the person is now on a very senior positron and if he needs to move more in his career he needs the experience letter.One more thing the owner of the company is directly involved in this matter and he is refusing again and again the experience letter.